Electronic device, method and computer-readable medium for sensing spectrum usage in a cognitive radio communication system

ABSTRACT

The disclosure provides an electronic device, a method and computer-readable medium. The electronic device includes a circuitry. The circuitry is configured to receive a radio communication signal for another device. The circuitry is also configured to determine, based on the radio communication signal, one or more features that can reflect the difference between uplink transmission mode and downlink transmission mode. The circuitry is further configured to judge whether the radio communication signal is for uplink transmission or downlink transmission according to the feature(s).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and is based upon and claims thebenefit of priority under 35 U.S.C. §120 from U.S. patent applicationSer. No. 15/219,765, filed Jul. 26, 2016, which is a continuation ofSer. No. 14/349,212, filed Apr. 2, 2014, (now U.S. Pat. No. 9,445,287)which is a National Stage Application of PCT/CN2012/082487, filed Sep.29, 2012, and claims the benefit of priority under 35 U.S.C. §119 ofChinese Patent Application No. 201110323808.X, filed Oct. 14, 2011; theentire contents of each of which are incorporated herein by reference.

FIELD OF THE INVENTION

The disclosure relates to the field of communication, and particularlyto a cognitive radio communication system, an apparatus and a methodused therein.

BACKGROUND OF THE INVENTION

Under a scenario of cognitive radio (CR), in order to allow a secondarysystem (SS) without a licensed spectrum to have an opportunity to accessa licensed spectrum of a primary system (PS), the primary system needsto have a capability of discovering a spectrum usage. A user in theprimary system (which is referred to as a secondary user (SU)) sensesthe spectrum being used by the primary system, judges whether there is aprimary user (PU) (i.e., a user in the primary system) signal, anddecides how to use the spectrum of the primary system withoutinterfering the PU.

SUMMARY OF THE INVENTION

The inventor of the present disclosure finds that: under certainscenario such as a cognitive radio scenario, a secondary system needs toknow about uplink/downlink configuration for a channel resource in aprimary system (i.e., whether each channel resource is used for uplinktransmission or downlink transmission) first, as the basis forsubsequent spectrum sensing and interference control. For example,taking a case that the primary system is a communication system based ontime division transmission (such as a time division duplex (TDD)communication system) as an example, transmission of an uplink channelresource and transmission of a downlink channel resource thereof areperformed alternatively in a time scale. The minimum duration foruplink/downlink transmission is generally referred to as a sub-frame.That is, under the cognitive radio scenario, a secondary user needs toknow about an uplink/downlink type of each sub-frame. In addition, inthe TDD system, several uplink/downlink sub-frames are combined into aframe, and the combination of the uplink/downlink sub-frames in eachframe is referred to as an uplink/downlink configuration. Generally,there can be many types of the uplink/downlink configurations (which isreferred to as “frame configuration”), and configurations of these typesare illustrated in detail in related communication standards.

In the prior art, it is generally assumed that the secondary system hasalready know about the uplink/downlink configuration for a channelresource in the primary system. For example, it is generally assumedthat the secondary system acquires uplink/downlink configurationinformation of the channel resource in the primary system by performinginformation interaction with the primary system. However, this does notcoincide with the requirements that the primary system cannot change itssystem setting and the secondary system is transparent to the primarysystem under the cognitive radio scenario. In addition, in a case thatthe primary system may actively transmit its channel resourceconfiguration information to the secondary system, there may be aselfish behavior that the primary system deliberately transmits errorinformation to prevent the secondary system from using the spectrum ofthe primary system.

Some embodiments of the disclosure provide an apparatus and a methodused in a cognitive radio system (i.e., a secondary system), with theapparatus or the method, the secondary system can acquireuplink/downlink configuration information of the channel resource in theprimary system without performing information interaction with theprimary system, thereby ensuring correctness of the information acquiredby the secondary system.

A brief summary regarding the disclosure is given hereinafter, toprovide basic understanding about some aspects of the disclosure. Itshould be understood that, this summary is not an exhaustive summaryabout the disclosure. This summary neither intends to determine acritical or important part of the disclosure, nor intends to limit thescope of the disclosure. The summary only aims at giving some conceptsin a simplified form as a preamble for description discussed later inmore detail.

According to one aspect of the disclosure, an apparatus used in acognitive radio communication system is provided. The apparatus mayinclude a receiving device, a feature extracting device, and anuplink/downlink judging device. The receiving device is adapted toreceive a communication signal between apparatuses in another radiocommunication system. The feature extracting device is adapted toextract, from the communication signal, one or more features that canreflect the difference between an uplink transmission mode and adownlink transmission mode of the another radio communication system.The uplink/downlink judging device is adapted to judge whether a channelresource occupied by the communication signal is used for uplinktransmission or downlink transmission according to the feature(s).

According to another aspect of the disclosure, a cognitive radio systemis provided, which may include the above apparatus. The above apparatusmay be equipped in a user apparatus in the cognitive radio system, or ina base station in the cognitive radio system.

According to yet another aspect of the disclosure, a method used in acognitive radio communication system is provided. According to themethod, a communication signal between apparatuses in another radiocommunication system is received. One or more features that can reflectthe difference between an uplink transmission mode and a downlinktransmission mode of the another radio communication system areextracted from the communication signal. A judgment is made as towhether a channel resource occupied by the communication signal is usedfor uplink transmission or downlink transmission according to thefeature(s).

According to yet another aspect of the disclosure, an electronic deviceis provided. The electronic device may include a circuitry. Thecircuitry is configured to receive a radio communication signal foranother device. The circuitry is also configured to determine, based onthe radio communication signal, one or more features that can reflectthe difference between uplink transmission mode and downlinktransmission mode. The circuitry is further configured to judge whetherthe radio communication signal is for uplink transmission or downlinktransmission according to the feature(s).

According to yet another aspect of the disclosure, a method used in aradio communication system is provided. According to the method, a radiocommunication signal for another device is received by a circuitry. Oneor more features that can reflect the difference between uplinktransmission mode and downlink transmission mode are determined by thecircuitry based on the communication signal. A judgment as to whetherthe radio communication signal is for uplink transmission or downlinktransmission is made by the circuitry according to the feature(s).

According to yet another aspect of the disclosure, a non-transitorycomputer-readable medium is provided. The non-transitorycomputer-readable medium is encoded with computer-readable instructionsthereon, the computer-readable instructions, when executed by acomputer, cause the computer to perform a method. According to themethod, a radio communication signal for another device is received. Oneor more features that can reflect the difference between uplinktransmission mode and downlink transmission mode are determined based onthe communication signal. A judgment as to whether the radiocommunication signal is for uplink transmission or downlink transmissionis made according to the feature(s).

In addition, an embodiment of the disclosure further provides a computerprogram for implementing the above method.

Further, an embodiment of the disclosure further provides a computerprogram product which is at least in the form of a computer readablemedium, with a computer program code recorded thereon for implementingthe above method.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the following illustration of embodiments of the disclosurethat is made in conjunction with the accompanying drawings, it will beeasier to understand the above and other objectives, characteristics andadvantages of the disclosure. Components in the accompanying drawingsare just used to illustrate the principle of the disclosure. In theaccompanying drawings, same or similar reference numbers are used toindicate same or similar technical characteristics or components.

FIG. 1 is a schematic flow chart of a method used in a cognitive radiosystem according to an embodiment of the disclosure;

FIG. 2 is a schematic flow chart of a method used in a cognitive radiosystem according to a specific embodiment;

FIG. 3 is a schematic diagram illustrating an application scenarioapplicable for the disclosure;

FIG. 4 is a schematic flow chart of a method used in a cognitive radiosystem according to another embodiment;

FIG. 5 is a chart illustrating frame configurations used in the TD-LTE(Time Division Long Term Evolution) standard;

FIG. 6 is a schematic flow chart illustrating an example of a method forcalculating a matching distance;

FIG. 7 is a schematic flow chart of a method used in a cognitive radiosystem according to another specific embodiment of the disclosure;

FIG. 8 is a schematic flow chart of a method used in a cognitive radiosystem according to another specific embodiment of the disclosure;

FIGS. 9(A), 9(B) and 9(C) respectively shows models for utilizingmultiple apparatuses in a cognitive radio system to detectuplink/downlink configuration for a channel resource in another radiosystem;

FIG. 10 is a schematic block diagram illustrating the structure of anapparatus used in a cognitive radio system according to an embodiment;

FIG. 11 is a schematic block diagram illustrating the structure of anapparatus used in a cognitive radio system according to anotherembodiment;

FIG. 12 is a schematic block diagram illustrating the structure of acomputer for implementing an embodiment or an example of the disclosure;

FIGS. 13 and 14 are schematic diagrams respectively illustratingapplication scenarios of multiple primary system cells adoptingdifferent frequency reuse strategies;

FIG. 15 is a schematic diagram illustrating an example of a scenariowhere a secondary system is located in multiple primary system cells;and

FIG. 16 is a schematic diagram illustrating another example of ascenario where a secondary system is located in multiple primary systemcells.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the disclosure are illustrated hereinafter in conjunctionwith the accompanying drawings. Elements and features described in oneaccompanying drawing or one embodiment of the disclosure may be combinedwith elements and features shown in one or more other accompanyingdrawings or embodiments. It should be noted that, for the purpose ofclarity, representation and description of components and processingwhich are unrelated with the disclosure and have been known by thoseskilled in the art are omitted in the accompanying drawings an thespecification.

Embodiments of the disclosure provide an apparatus and a method used ina cognitive radio system (which is also referred to as a secondarysystem), so that the secondary system can acquire uplink/downlinkconfiguration information of a channel resource in another radiocommunication without performing information interaction with thatsystem. In the disclosure, the another radio communication system mayalso be referred to as a primary system, which may be any communicationsystem applicable for a cognitive radio scenario, for example, a radiocommunication system based on time division transmission (such as a TDDcommunication system), which is not enumerated here.

FIG. 1 is a schematic flow chart of a method used in a cognitive radiosystem according to an embodiment of the disclosure. In this method, anapparatus in the secondary system judges the uplink/downlinkconfiguration of a channel resource in the primary system according totransmission feature(s) of a communication signal in the primary system.

As shown in FIG. 1, the method may include steps 102, 104 and 106.

At step 102, an apparatus in the secondary system receives acommunication signal between apparatuses in the primary system. Here,the apparatus in the secondary system may be a user apparatus in thesecondary system (which is also referred to as a secondary user), andmay also be a base station apparatus in the secondary system.

At step 104, the apparatus in the secondary system extracts one or morefeatures from the received communication signal. The extracted featuresmay be any feature of an uplink/downlink communication signal in theprimary system which can reflect the difference between an uplinktransmission mode and a downlink transmission mode of the primarysystem. Thus, at step 106, the apparatus in the second system may judgewhether a channel resource occupied by the received communication signalof the primary system is used for uplink transmission or downlinktransmission, according to the extracted features. In other words, theapparatus in the secondary system can know about uplink/downlinkconfiguration for the channel resource in the primary system byanalyzing the received communication signal of the primary system.

The inventor of the disclosure finds that, in different communicationsystems, there may be some significant differences between an uplinkcommunication signal and a downlink communication signal. For example,the transmission powers adopted in an uplink signal and a downlinksignal are different. Typically, the transmission power of the downlinksignal is significantly higher than that of the uplink signal. In thiscase, the apparatus in the secondary system may extract, from thecommunication signal of the primary system, a feature capable ofreflecting the transmission power of the communication signal, therebyjudge whether the channel resource occupied by the communication signalis used for the uplink transmission or the downlink transmission. Theapparatus in the secondary system may extract, from the communicationsignal, the feature reflecting the transmission power of thecommunication signal with any suitable method, for example, an energydetection method described later with reference to FIG. 2 or Formulas(1) to (3), which is not illustrated here in detail.

As another example, in some communication systems, the modulation modesadopted for the uplink signal and the downlink signal are different.Therefore, the apparatus in the secondary system may extract, from thecommunication signal of the primary system, a feature capable ofreflecting the modulation mode for the communication signal as thefeature. Any suitable method may be adopted to extract, from thecommunication signal, the feature reflecting the modulation mode for thecommunication signal, for example, a wavelet transform algorithm forrecognizing the modulation mode or the like may be utilized to extractthe feature reflecting the modulation mode, which is not illustratedhere in detail.

As another example, in some communication systems, the peak-to-averageratio of the uplink signal is different from that of the downlinksignal. In this case, the apparatus in the secondary system maycalculate a peak-to-average ratio according to the communication signalof the primary system as the feature, to judge whether the channelresource occupied by the communication signal is used for the uplinktransmission or the downlink transmission.

In a specific embodiment, the apparatus in the secondary system mayextract, from the communication signal of the primary system, any one ofa feature reflecting the transmission power, a feature reflecting themodulation mode or a peak-to-average ratio, as the feature. As ananother specific embodiment, the apparatus in the secondary system mayextract two or more of the above features from the communication signalof the primary system, and utilize the extracted two or more features tojudge whether the channel resource occupied by the communication signalis used for the uplink transmission or the downlink transmission,thereby making subsequent judgment result more accurate.

In addition, it should be understood that, the features described aboveare exemplary but not exhaustive. Any other feature capable ofreflecting the difference between the uplink transmission mode and thedownlink transmission mode for the primary system may be adopted, whichis not limited to the features listed above.

In the method described above with reference to FIG. 1, the apparatus inthe secondary system judges the uplink/downlink configuration for thechannel resource in the primary system by utilizing the receivedcommunication signal from the primary system. With this method, there isno need for the apparatus in the secondary system to perform informationinteraction with an apparatus in the primary system, therefore, there isno need for the primary system to change its system configuration, whichcan better meet the requirement that the secondary system is transparentto the primary system under the cognitive radio scenario.

Some specific embodiments according to the disclosure will be describedin the following.

FIG. 2 shows a specific embodiment of a method used in a cognitive radiosystem according to the disclosure. In the specific embodiment, theapparatus in the secondary system may extract, from the communicationsignal of the primary system, a feature reflecting the transmissionpower of the communication signal, for judging the uplink/downlinkconfiguration for the channel resource in the primary system.

As shown in FIG. 2, at step 202, the apparatus in the secondary systemreceives a communication signal between apparatuses in the primarysystem. Then, at step 203, the apparatus in the secondary system mayextract synchronization information in the received communication signalto locate channel resources occupied by the communication signal. Takinga case that the primary system is a communication system based on timedivision transmission as an example, after receiving the communicationsignal of the primary system, the apparatus in the secondary system mayfirst locate a sub-frame header and a frame header. Here, the frame andthe sub-frame are the channel resources, the sub-frame header and theframe header respectively indicate a boundary between sub-frames and aboundary between frames, and locating the channel resources meanslocating the boundaries between the frames and boundaries between thesub-frames. Here, the secondary system needs to have priori knowledgeabout definition for a synchronization signal and definition forsynchronous timing in related communication standards of the primarysystem. These priori knowledge may be pre-stored in a storage device(not shown in the figure) of the apparatus in the secondary system. Thesecondary system may utilize the synchronization signal defined in thecommunication standard of the primary system to perform circularcorrelation detection with a primary user signal, and locate thestarting time of each sub-frame and the staring time of each frame incombination with the synchronous timing defined in the communicationstandard. It can be understood by those skilled in the art, any suitablemethod may be adopted to perform the circular correlation detection,which is not illustrated here in detail. In addition to the above prioriknowledge, other priori knowledge is not needed by the apparatus in thesecondary system in performing the circular correlation detection.Generally, only several radio frames are needed for the apparatus in thesecondary system to implement a synchronizing process of the sub-framesand frames. The locating process of the sub-frame headers and the frameheaders are similar to the synchronizing processes in initialization ofthe primary system, which are not illustrated here in detail.

Then, at step 204, the apparatus in the secondary system may estimatethe energy value of the communication signal in the channel resource itoccupied in the primary system, as the feature for judging theuplink/downlink configuration for the channel resource. Any suitablemethod may be adopted to estimate the energy value of the communicationsignal (for example, an example described later with reference toFormulas (1) to (3)) as the feature reflecting the transmission power ofthe communication signal, which is not illustrated here in detail.Subsequently, at step 206, the apparatus in the secondary system judgeswhether a predetermined relationship is satisfied between the estimatedenergy value and a predetermined threshold value (which is referred toas a first threshold value), and if yes, then judges that the channelresource is used for the downlink transmission; otherwise, judges thatthe channel resource is used for the uplink transmission. Generally, thedownlink transmission generally adopts constant power; and for theuplink transmission, since the number of the primary users, the numberof allocated sub-carriers, the allocated power and the like aredifferent, the magnitudes of uplink transmission power are different.However, the downlink transmission power is always much larger than theuplink transmission power. In order to distinguish the downlinktransmission and the uplink transmission, an extreme case that thetransmission power of the uplink transmission is maximum (i.e., a casethat all sub-carriers are allocated) need to be considered, to moreaccurately distinguish the uplink transmission and the downlinktransmission. Therefore, the apparatus in the secondary system may setthe first threshold value according to the downlink transmission powerand the maximum uplink transmission power of the primary system. Forexample, any value between the downlink transmission power and themaximum uplink transmission power (such as an average value thereof or amid-value therebetween) may be set as the first threshold value. Whenthe estimated energy value is larger than the first threshold value, itcan be judged that the channel resource is used for the downlinktransmission; otherwise, it can be judged that the channel resource isused for the uplink transmission. It should be understood that, indifferent application scenarios, the downlink transmission power as wellas the maximum uplink transmission power of the primary system may bedifferent, therefore, the specific value of the predetermined thresholdvalue is not specifically defined here. In addition, information aboutthe downlink transmission power and the maximum uplink transmissionpower of the primary system and the like may be stored, as the prioriknowledge, in a storage device (which is not shown in the figure) of theapparatus in the secondary system or in a storage device which isseparate from the apparatus in the secondary system but accessible bythe apparatus in the secondary system, which is not described here indetail.

In the specific embodiment described above, the apparatus in thesecondary system judges the uplink/downlink configuration for thechannel resource in the primary system by utilizing the differencebetween the uplink transmission power and the downlink transmissionpower. In addition to the downlink transmission power and the maximumuplink transmission power of the primary system, the secondary systemdoes not need to acquire other priori knowledge about the primary systemfor judging the uplink/downlink configuration, thereby facilitating thedeployment of the secondary system.

Optionally, after the apparatus in the secondary system estimates theenergy value of the communication signal in the channel resource itoccupied in the primary system and judges that the channel resource isused for the uplink transmission by utilizing the estimated energyvalue, the apparatus in the secondary system may further judge whetherthe uplink channel resource is idle (such as the step shown in thedashed line block 208 in FIG. 2).

Taking the application scenario shown in FIG. 3 as an example, it isassumed that the primary system is a communication system based on timedivision transmission. As shown in FIG. 3, it is assumed that there isone primary system (PS) and one secondary system (SS) in the applicationscenario. The primary system includes one primary base station (PSB) andn_(pu) primary users (PU), and the secondary system includes onesecondary base station (SBS) and n_(su) secondary users (SU). Thesecondary system tries to use a channel resource in the primary systemthat is close to the secondary system. Here, it is assumed that thesecondary system is at the edge of the primary system cell, the primaryusers are randomly distributed within the primary system having a cellradius of R_(ps), and the secondary users are randomly distributedwithin the secondary system having a cell radius of R_(ss).

It is assumed that the primary system is a communication system adoptingTD-LTE (Time Division Long Term Evolution) standard, and 10 sub-framesare included in each frame, i.e., n_(sf)=10. The apparatus in thesecondary system needs to detect the uplink/downlink configurations forthe 10 sub-frames in each frame, that is, judge whether each sub-framein the frame is used for uplink transmission or downlink transmission.As a specific example, the apparatus in the secondary system mayestimate an energy value of each received sub-frame with an energydetection method. In this instance, a method that performs Fast FourierTransform (FFT) on the received communication signal is used to acquirea sample of each symbol on a sub-carrier. Assuming that n_(id) secondaryusers detect the uplink/downlink configuration for each sub-framesimultaneously, and s_(i)[l, k] (1≦i≦n_(id)) is the sample of an l-thsymbol on a k-th sub-carrier that is received by an i-th secondary user(which is indicated as su_(i)), then the following formula may beobtained:

$\begin{matrix}{{s_{i}\left\lbrack {l,k} \right\rbrack} = \left\{ \begin{matrix}{{{{h_{i}^{(d)}\left\lbrack {l,k} \right\rbrack}{s^{(d)}\left\lbrack {l,k} \right\rbrack}} + {n_{i}\left\lbrack {l,k} \right\rbrack}},} & {{downlink}\mspace{14mu} {sub}\text{-}{carrier}} \\{{{{h_{i}^{(u)}\left\lbrack {l,k} \right\rbrack}{s^{(u)}\left\lbrack {l,k} \right\rbrack}} + {n_{i}\left\lbrack {l,k} \right\rbrack}},} & {{uplink}\mspace{14mu} {sub}\text{-}{carrier}\mspace{14mu} ({occupied})} \\{{n_{i}\left\lbrack {l,k} \right\rbrack},} & {{uplink}\mspace{14mu} {sub}\text{-}{carrier}\mspace{14mu} \left( {{un}\text{-}{occupied}} \right)}\end{matrix} \right.} & (1)\end{matrix}$

In the above formula, s^((d)) [l, k] and s^((u)) [l, k] respectivelyindicate transmitted samples of the l-th symbol on the k-th sub-carrierfor a downlink signal and an uplink signal, n_(i)[l, k] indicates anoise sample received by su_(i), h_(i) ^((u))[l, k] indicates a channelgain between a transmitter corresponding the uplink signal and su_(i),and h_(i) ^((d)) [l, k] indicates a channel gain between a transmittercorresponding the downlink signal and su_(i). Three states of the signalshown in Formula (1) indicate downlink transmission (which is alwayspresent on each useful sub-carrier), uplink transmission (the uplinksub-carrier is occupied by the primary user) and uplink but idle (thatis, the sub-carrier is not occupied by the primary user, and only anenvironmental noise is present), respectively.

The secondary user may accumulate energy of the first n_(s) symbols ofeach sub-frame, and calculate an average value thereof as an energyestimation value T_(i) of each sub-frame, that is:

$\begin{matrix}{T_{i} = {\frac{1}{n_{s}N_{sc}}{\sum\limits_{k = 1}^{n_{s}}{\sum\limits_{l = 1}^{N_{sc}}{{s_{i}\left\lbrack {l,k} \right\rbrack}}^{2}}}}} & (2)\end{matrix}$

In Formula (2), N_(sc) is the number of sub-carriers used in energydetection. In order to reduce the number of the symbols used indetection, it may be assumed that N_(sc) is the number of allsub-carriers in a frequency band of the primary system. As describedabove, the downlink transmission of the primary system are alwaysperformed with constant power; and for the uplink transmission, sincethe number of the primary users, the number of the allocatedsub-carriers, the allocated power and the like are different, the totalpower of the uplink transmission is different. In order to distinguishthe downlink transmission and the uplink transmission, an extreme casethat the transmission power of the uplink transmission is maximum (i.e.,a case that all sub-carriers are allocated) needs to be considered, tomore accurately distinguish the uplink transmission and the downlinktransmission. The following formula may be obtained by combining theformulas (1) and (2):

$\begin{matrix}{T_{i} = \left\{ \begin{matrix}{\frac{1}{n_{s}N_{sc}}{\sum\limits_{k = 1}^{n_{s}}{\sum\limits_{l = 1}^{N_{sc}}\left\{ {{{{h_{i}^{(d)}\left\lbrack {l,k} \right\rbrack}{s^{(d)}\left\lbrack {l,k} \right\rbrack}}}^{2} + {{n_{i}\left\lbrack {l,k} \right\rbrack}}^{2}} \right\}}}} & {downlink} \\{\frac{1}{n_{s}N_{sc}}{\sum\limits_{k = 1}^{n_{s}}{\sum\limits_{l = 1}^{N_{sc}}\left\{ {{{{h_{i}^{(u)}\left\lbrack {l,k} \right\rbrack}{s^{(u)}\left\lbrack {l,k} \right\rbrack}}}^{2} + {{n_{i}\left\lbrack {l,k} \right\rbrack}}^{2}} \right\}}}} & {uplink} \\{\frac{1}{n_{s}N_{sc}}{\sum\limits_{k = 1}^{n_{s}}{\sum\limits_{l = 1}^{N_{sc}}{{n_{i}\left\lbrack {l,k} \right\rbrack}}^{2}}}} & {{uplink}\mspace{14mu} {but}\mspace{14mu} {idle}}\end{matrix} \right.} & (3)\end{matrix}$

In Formula (3), “downlink” indicates the downlink transmission (which isalways present on each useful sub-carrier), “uplink” indicates theuplink transmission ((the uplink sub-carrier is occupied by the primaryuser), and “uplink but idle” indicates the uplink but idle state (i.e.,the sub-carrier is not occupied by the primary user, and only anenvironmental noise is present). It is assumed that the three states arerespectively indicated as

_(d),

_(u) and

_(i), in which both

_(u) and

_(i) are in the uplink transmission state.

The above formula can show that the three states may be distinguishedaccording to the magnitude of the estimated energy values, therebyjudging the uplink/downlink configuration for the channel resource.Specifically, a value between the downlink transmission power and themaximum uplink transmission power of the primary system may be used asthe first threshold value for distinguishing the uplink transmission andthe downlink transmission (as described above with reference to step204). In addition, after it is judged that the channel resource (such aseach sub-frame) is used for the uplink transmission, any suitable valuebetween the uplink transmission power of the primary system and anenvironment background noise statistic (it should be understood by thoseskilled in the art that, any suitable method may be used to obtain theenvironment background noise statistic, which is not described here indetail) as a second threshold value. The apparatus in the secondarysystem may further judge whether a predetermined relationship issatisfied between the estimated energy value and the second thresholdvalue, and if it is judged that the predetermined relationship issatisfied between the estimated energy value and the second thresholdvalue, then it is judged that the channel resource is idle. For example,if the estimated energy value is less than or equal to the secondthreshold value, then it is judged that the channel resource is idle;otherwise, it is judged that the channel resource is not idle.

Still taking the application scenario shown in FIG. 3 as an example, aspecific example for determining the first threshold value and thesecond threshold value will be described in the following.

As described above, the

_(i) state only includes complex noise signals on the N_(sc)sub-carriers. Assuming that N_(d) indicates noise power spectral densityof a primary system channel, and B_(s) indicates bandwidth of eachsub-carrier, then Var_(n)=N_(sc)N_(d)B_(S) is noise power of the primarysystem channel. It is assumed that T_(th) ^(l) indicates the secondthreshold value, then T_(th) ^(l) may be set as a value which is onlyrelated to the noise to distinguish the

_(u) and

_(i) states of the uplink channel resource. According to an energydetection theory, the threshold value may be set as:

T th l = Var n   ( 1 + - 1  ( p f i ) n s  N sc / 2 ) ( 4 )

In the above formula, p_(ƒ) ^(i) indicates the probability that thedetection statistic is larger than T_(th) ^(l), i.e., the probabilitythat the

_(i) state is detected as the

_(u) or

_(d) state by mistake, and

(•) indicates an inverse Q function. Any suitable method may be adoptedto determine the probability p_(ƒ) ^(i), for example, the probabilitymay be predetermined as a small probability, such as 10% or a value lessthan 10%, which is not described here in detail.

In addition, it is assumed that the first threshold is indicated asT_(th) ^(h). The first threshold value T_(th) ^(h) is larger than thesecond threshold value, which may be set with reference to thedefinition related to the uplink transmission power and downlinktransmission power in the communication standards of the primary systemas described above. As an example, T_(th) ^(h) may be less than theaverage received power of a downlink signal, and larger than the averagereceived power of an uplink signal. As another example, T_(th) ^(h) maybe set according to a mid-value between the average received power thata receiver in the secondary system receives the uplink signal and theaverage received power that the receiver in the secondary systemreceives the downlink signal. As another example, T_(th) ^(h) may be setfrom the perspective of error detection probability. A T_(th) ^(h)determination method based on the error detection probability isillustrated hereinafter in detail.

As described above, the base station in the primary system alwaysperforms the downlink transmission with constant power P_(d), whereasthe transmission power of each primary user is related to the powerallocated thereto. Therefore, when all the primary users perform theuplink transmission with the maximum power, an uplink communicationsignal and a downlink communication signal of the primary system aremost likely to be confused with each other. Therefore, the firstthreshold value T_(th) ^(h) may be set according to the maximum uplinktotal power and the downlink total power. It is assumed that P_(u)^(max) indicates uplink maximum total transmission power, then P_(u)^(max)=n_(pu) ^(max)P_(pu) ^(max), where n_(pu) ^(max) indicates themaximum number of the primary users supported by the primary system, andp_(pu) ^(max) indicates maximum transmission power of each primary userin the primary system. Since the primary users and the secondary usersare randomly distributed within a certain region, each secondary usermay receive a different average energy value of the uplink signal and adifferent average energy value of the downlink signal. The firstthreshold value may be set by considering an average case, that is,assuming that the primary user and the secondary user are respectivelylocated at the centre of the primary system and the centre of thesecondary system, then the first threshold value T_(th) ^(h) may bedefined as follows:

T th t = ( Var n + PL R ps  P u max )  ( 1 + - 1  ( p f u ^ ) n s  Nsc / 2 ) ( 5 )

In the above formula, PL_(R) _(ps) indicates path loss from the centreof the primary system to the centre of the secondary system (i.e., theedge of the primary system), and {circumflex over (p)}_(f) ^(u)indicates the referred probability that the

_(u) state is detected as the

_(d) state by mistake, it should be noted that the probability{circumflex over (p)}_(f) ^(u) is not an actual probability but areference value. Any suitable method may be adopted to determine theprobability {circumflex over (p)}_(f) ^(u), for example, the probabilitymay be predetermined as a small probability, such as 10% or a value lessthan 10%, which is not described here in detail. The probability{circumflex over (p)}_(m) ^(d) that the

_(d) state is detected as the

_(u) state by mistake may be determined with the following formula:

p m d ^ = 1 -  ( - 1  ( p f u ^ ) - λ d - u  n s  N sc / 2 1 + λ d -u ) ( 6 )

Wherein λ_(d-u) indicates a signal-to-noise ratio of the downlink signalto the uplink signal, i.e.,

$\begin{matrix}{\lambda_{d - u} = {\frac{{P_{d}{PL}_{R_{ps}}} + {Var}_{n}}{{P_{u_{\max}}{PL}_{R_{ps}}} + {Var}_{n}} - 1}} & (7)\end{matrix}$

The above Formula (4) shows that the second threshold value T_(th) ^(l)is related to the noise power on the frequency band of the primarysystem (PS), but unrelated to signal features of the primary system.Compared with the second threshold value T_(th) ^(l), the setting forthe first threshold value T_(th) ^(h) is relatively complicated.

Other specific examples for determining the first threshold value T_(th)^(h) in some specific application scenarios will be describedhereinafter.

For example, the first threshold value may be determined according towhether the secondary system can acquire information about relativepositions (such as distances between respective nodes) between alltransceivers (i.e., all nodes) in the primary system and the secondarysystem. For example, if the secondary system can know about the relativeposition information (i.e., a case that the relative positions betweenrespective nodes can be located), then the secondary system may estimateaccuracy of the uplink/downlink detection, thereby accurately settingthe first threshold value according to the accuracy. Alternatively, ifthe secondary can know about a maximum value or a minimum value of therelative position information, the secondary system may estimate amaximum value or a minimum value of the uplink/downlink detectionaccuracy, and calculate a feasible search interval of the firstthreshold value, thereby searching a suitable value within the searchinterval as the first threshold value. And if the secondary system cannot know about the relative position information (i.e., a case that therelative positions between respective nodes can not be located), thefirst threshold value may be set according to the maximum uplinktransmission power and the downlink transmission power of the primarysystem as described above.

As a specific example, assuming that the secondary system is located ina single primary system cell and the secondary system can know aboutdistances between all transceivers in the primary system and thesecondary system (i.e., all nodes in the primary system and thesecondary system) (the secondary base station may adopt any suitablemethod to locate the relative positions between all nodes, which is notdefined and described here in detail).

In a case of the single primary system cell, the secondary system iscommonly located at the edge of the primary system cell. The detectionstatistic on the secondary user is only influenced by the single primarysystem cell.

Under the assumption of a Gaussian channel and a Rayleigh channel, inthe

and

states, the statistic in the above formula (2) may be replaced with adetection signal-to-noise ratio, that is:

$\begin{matrix}{T_{i} = {{\frac{1}{n_{s}N_{sc}}{\sum\limits_{k = 1}^{n_{s}}{\sum\limits_{l = 1}^{N_{sc}}{{s_{i}\left\lbrack {l,k} \right\rbrack}}^{2}}}} = {{\sum\limits_{k = 1}^{n_{sc}}{\sum\limits_{l = 1}^{N_{sc}}{\frac{\left( {\lambda_{({k,l,i})} + 1} \right)}{2n_{s}N_{sc}}{\chi^{2}(2)}}}} = {\sum\limits_{m = 1}^{P}{c_{m}{\chi^{2}(2)}}}}}} & ({A1})\end{matrix}$

Wherein X²(2) indicates a chi-square variable whose degree of free is 2,p=n_(s)N_(sc) indicates the number of samples used in detection, and

$c_{m} = \frac{\lambda_{({k,l,i})} + 1}{2p}$

(where λ_((k,l,i)) is the detection signal-to-noise ratio of su_(i) to ak-th symbol of an l-th sub-carrier). It can be known from the Formula(A1) that, c_(m) is related to transmitter (which is a transmitter of aprimary user in an uplink direction, and is a transmitter of a primarybase station in a downlink direction) power of the primary system, adistance between the transmitter and the secondary user su_(i) and otherfactors, therefore, the detection statistic for each secondary user isdifferent from each other.

It is assumed that d_(i) indicates a distance between the secondary usersu_(i) and the primary base station (PBS), b_(j) indicates a distancebetween the primary user pu_(j) (j=1, . . . , n_(pu)) and the primarybase station, and c_(j,i) indicates a distance between pu_(j) andsu_(i). Based on the above distance information and an energy detectiontheory, the error detection probability p_(1ƒ) ^((i)) that the

state is detected as the

or

state by the su_(i) may be estimated with the following formula:

p 1  f ( i ) = Pr  ( T i ≤ T th t  d  , d i ) = Φ  ( T th h - 2 cp c  2  p ) ( A2 )

Wherein c indicates a power coefficient of each sample in Formula (A1),which represents the power of each sample. Since in a case of thedownlink transmission, the power of each sample is the same, so

${c = {c_{1} = {\ldots = {c_{m} = {\ldots = {c_{p} = {\frac{\lambda_{({k,l,i})} + 1}{2p} = {{\left( {\frac{P_{d}}{{Var}_{n}{PL}_{di}} + 1} \right)/2}p}}}}}}}},$

wherein c_(l), c_(m) and c_(p) respectively indicate power coefficientsof the samples, and PL_(d) _(i) , indicates path loss between su_(i) andthe primary base station. p indicates the number of samples used in thedetection. Pr(x) indicates probability of an event x. Φ(x) indicates acumulative distribution function (CDF) in normal distribution.

Q _(1ƒ)=ƒ_(c)(p _(1ƒ) ⁽¹⁾ , . . . p _(1ƒ) ^((i)) , . . . ,p _(1ƒ) ^((n)^(su) ⁾)  (A3)

Wherein Q_(1ƒ) indicates a decision strategy, which indicatesperformance measure of the whole algorithm, and is detection errorprobability that the downlink transmission is judged as the uplinktransmission. ƒ_(c)( ) indicates a cooperative and fused performancefunction, and an independent variable of the performance function (i.e.,each parameter in ( )) is the detection error probability of eachsecondary user. According to the above Formulas (A2) and (A3), Q_(1ƒ)values under different T_(th) ^(h) values may be calculated, i.e.,sub-frame detection performance in the

_(d) state is obtained: the detection error probability that the

_(d) state is detected as the

_(u) or

_(i) state by the secondary base station (SBS) when the link is in the

_(d) state. According to correspondence between T_(th) ^(h) and Q_(1ƒ),a value range of T_(th) ^(h) satisfying Q_(1ƒ)≦Q_(1ƒ) ^(d) may beobtained (wherein Q_(1ƒ) ^(d) indicates a maximum value of Q_(1ƒ)in the

_(d) state), that is:

$\begin{matrix}{T_{th}^{h} = \frac{{{\Phi^{- 1}\left( p_{1f}^{(i)} \right)}P_{d}\sqrt{2p}} + {2{pP}_{d}}}{{Var}_{n}{PL}_{d_{i}}}} & ({A4})\end{matrix}$

Wherein Φ⁻¹(x) indicates an inverse function of the cumulativedistribution function in normal distribution.

As can be known from the above Formula (A4), p_(1ƒ) ^((i)) needs to besmall enough, i.e., T_(th) ^(h) needs to be less than a specific value,to satisfy the detection performance in the

_(d) state. In a case that the maximum value of p_(1ƒ) ^((i)) if can becalculated, the specific value may be directly acquired.

If it is difficult for the decision strategy Q_(1ƒ)=ƒ_(c)( ) to have aclosed-form solution, i.e., it is difficult to acquire a correspondencebetween T_(th) ^(h) and Q_(1ƒ), then T_(th) ^(h) may be estimated withthe following formula:

$\begin{matrix}{T_{th}^{h} \leq {\max\limits_{i}\frac{{{\Phi^{- 1}\left( p_{1f}^{(i)} \right)}P_{d}\sqrt{2p}} + {2{pP}_{d}}}{{Var}_{n}{PL}_{d_{i}}}} \approx \frac{{{\Phi^{- 1}\left( \overset{\_}{p_{1f}} \right)}P_{d}\sqrt{2p}} + {2{pP}_{d}}}{{Var}_{n}{PL}_{\min \; d_{i}}}} & ({A5})\end{matrix}$

Wherein p_(1ƒ) indicates average detection error probability of a singlesecondary user, and

${\overset{\_}{p_{1f}} = \left( Q_{1f}^{d} \right)^{\frac{1}{n_{su}}}},{PL}_{\min \; d_{i}}$

indicates path loss between a secondary user closet to the primary basestation and the primary base station in the system. Formula (A5)considers a case that T_(th) ^(h) has a maximum value when the secondarybase station finally judges that the current sub-frame or the currentlink is in the

_(d) state as long as one secondary user detects that it is in the

_(d) state (which is also referred to as an OR criterion). It can beseen that the maximum value of T_(th) ^(h) here is determined by thesecondary user closet to the primary base station. In Formula (A5),p_(1ƒ) ^((i)) in Formula (A4) may be approximately replaced with anaverage value

$\overset{\_}{p1f}\; = \left( Q_{1f}^{d} \right)^{\frac{1}{n_{su}}}$

of local (i.e., a single secondary user) detection error probabilityunder the OR criterion.

Similarly, assuming that the error probability that the

_(u) state is detected as the

_(d) or

_(i) state by su_(i) is p_(0ƒ) ^((i)), then:

p 0  f ( i ) =  Pr  ( T i ≥ T th h , T i ≤ T th l  u , b 1 , …  , bn su , c 1 , i , …  , c n su , i ) =  1 - Φ  ( T th h - ∑ j  2  c j∑ j  2  c j 2 ) + Φ  ( T th l - ∑ j  2  c j ∑ j  2  c j 2 )   (A6 )

Wherein b₁, . . . , b_(n) _(uc) respectively indicate the distancebetween each primary user and the primary base station, and c_(1,i), . .. , c_(n) _(uc) _(,i) respectively indicate the distance between eachprimary user and each secondary user. Assuming that each primary user inthe primary system is allocated with sub-carriers having the same number

$\frac{N_{sc}}{n_{pu}},$

then:

$\begin{matrix}{c_{{{{({\frac{N_{sc}n_{s}}{n_{pu}} - 1})}j} + 1},\ldots \mspace{14mu},{\frac{N_{sc}n_{s}}{n_{pu}}j}} = {\frac{\lambda_{({k,l,i})} + 1}{2p} = \frac{\frac{P_{0}{PL}_{b_{j}}}{{PL}_{c_{j,i}}} + 1}{2p}}} & ({A7})\end{matrix}$

Wherein PL_(b) _(j) and PL_(c) _(j,i) respectively indicate path lossbetween pu_(j) and the primary base station and path loss between pu_(j)and su_(i). If an AND criterion is adopted, i.e., the secondary basestation judges that it is in the

_(d) state only if all secondary users detect that it is in the

_(d) state, then the T_(th) ^(h) may have a minimum value, that is,

$\begin{matrix}{T_{th}^{h} \geq {\max\limits_{i,j}\left( {{{\Phi^{- 1}\left( {1 + {\Phi\left( \frac{T_{th}^{l} - {\sum_{j}{2c_{j}}}}{\sum_{j}{2c_{j}^{2}}} \right)} - p_{0f}^{(i)}} \right)}{\sum\limits_{j}{2c_{j}^{2}}}} + {\sum\limits_{j}{2c_{j}}}} \right)} \approx {\max\limits_{j}\left( {{{\Phi^{- 1}\left( {1 + {{\Phi\left( \frac{T_{th}^{l} - {\sum_{j}{2c_{j}}}}{\sum_{j}{2c_{j}^{2}}} \right)}{- \overset{\_}{p_{0f}}}}} \right)}{\sum\limits_{j}{2c_{j}^{2}}}} + {\sum\limits_{j}{2c_{j}}}} \right)}} & ({A8})\end{matrix}$

Wherein

${\overset{\_}{p_{1f}} = \left( Q_{1f}^{d} \right)^{\frac{1}{n_{su}}}},$

which indicates an average value of the detection error probability bythe secondary user under the AND criterion, Q_(0ƒ) ^(d) indicates amaximum value of Q_(0ƒ) in the

state; and Q_(0ƒ) indicates the actual detection performance measure ofthe algorithm, representing the detection error probability that theuplink transmission is detected as the downlink transmission. Themaximum value Q_(0ƒ) ^(d) may be acquired according to relativepositions in a network (here, the primary system and the secondarysystem are regarded as a network, and the relative positions in thenetwork indicates relative positions between all notes in the primarysystem and the secondary system).

According to Formulas (A5) and (A8), a feasible search interval ofT_(th) ^(h) (i.e., a possible range including the maximum value and theminimum value of the threshold value) may be obtained. Thus obtainedsearch interval is relatively large. In order to enhance the searchspeed, the searching may be performed near an approximate value ofT_(th) ^(h) (such as an approximate value calculated with the aboveFormula (5)) (specifically, the value of T_(th) ^(h) may be changed, andthe value of Q_(1ƒ) and the value of Q_(0ƒ) are estimated underdifferent values of T_(th) ^(h), thereby an optimum value of T_(th) ^(h)may be searched), thereby acquiring the value of T_(th) ^(h).Optionally, any value within the feasible search interval may be used asthe threshold value T_(th) ^(h).

As another specific example, it is assumed that the secondary system islocated in a single primary system cell and that the secondary system isunable to know about distances between transceivers in the primarysystem and the secondary system, that is, the secondary system is unableto locate the distances between the transceivers in the primary systemand the secondary system.

In such a case in which it is unable to locate, the secondary basestation is difficult to acquire relative position information about theprimary system and the secondary system, therefore, it is difficult toacquire accurate values of p_(1ƒ) ^((i)) and p_(0ƒ) ^((i)). In thiscase, the first threshold value T_(th) ^(h) may be set with asemi-simulation method: that is, a simulation method is adopted togenerate enough relative positions between the transceivers in theprimary system and the secondary system (any suitable method may beutilized to simulate the relative positions between respectivetransceivers in the primary system and the secondary system, forexample, the simulation may be performed according to a common model ofnode distribution (such as uniform distribution or Poisson distribution)in the network, which is not defined and described here in detail), andvalues of Q_(1ƒ) and Q_(0ƒ) are calculated under different T_(th) ^(h),and thereby obtaining a T_(th) ^(h) satisfying requirements of Q_(1ƒ)and Q_(0ƒ), that is:

$\begin{matrix}{Q_{1f} \approx {\sum\limits_{sim}^{N_{sim}}\frac{q_{1f}^{({sim})}}{N_{sim}}}} & (9) \\{Q_{0f} \approx {\sum\limits_{sim}^{N_{sim}}\frac{Q_{0f}^{({sim})}}{N_{sim}}}} & (10)\end{matrix}$

Wherein q_(1ƒ) ^((sim)) and q_(0ƒ) ^((sim)) respectively indicatesub-frame performance measure values Q_(1ƒ) and Q_(0ƒ) that arecalculated by utilizing the relative positions obtained in thesimulation, and N_(sim) indicates the number that the simulation isperformed. With the value of Q_(1ƒ) and the value of Q_(0ƒ) obtainedwith the above Formulas (A9) and (A10) (i.e., the values of theright-hand side of the formulas (A9) and (A10)), a suitable value of TAmay be obtained according to the detection performance requirements.

In such an application in which it is unable to locate, the searchinterval described above is not applicable. That is, in a case that itis unable to locate, the search interval of the threshold value can notbe estimated with Formulas (A5) to (A8). If Formula (5) is adopted, thenthere is no need to adopt the technology described in Formulas (A5) to(A8). As described above, a value between the downlink transmissionpower and the maximum uplink transmission power of the primary systemmay be set as the first threshold value, for example, an approximatevalue calculated with the formula (5) may be adopted.

Two examples in which the secondary system is located in a singleprimary system cell have been described above. In an environment ofmultiple primary system cells, the detection statistic of the secondaryuser is related to the multiple primary system cells. When the multipleprimary system cells coexist, transmission power control and frequencyallocation are key factors that affect the statistic, and which aremainly decided by a frequency reuse (FR) strategy. For example, when theprimary system is a TD-LTE system, two common FR strategies includefractional frequency reuse (FFR) and soft frequency reuse (soft FR).

FIG. 13 is a schematic diagram illustrating the strict FFR strategy. InFIG. 13, each hexagonal block indicates one primary system cell. In eachhexagonal block, the circular region indicates the centre of the primarysystem cell, and the remaining part other than the circular regionindicates the edge of the primary system cell. Under this strategy, ineach primary system cell, users located at the centre of the cells areallocated with a same frequency band F_(center). Users located at theedges of respective primary system cells use different frequency bands,and these frequency bands are not overlapped with F_(center). As shownin the figure, F_(edge) ₁ indicates a frequency band used by a userlocated at the edge of a primary system cell 1; F_(edge) ₂ indicates afrequency band used by a user located at the edge of a primary systemcell 2, 4 or 6; and F_(edge) ₂ indicates a frequency band used by a userlocated at the edge of a primary system cell 3, 5 or 7.

${F_{center} = \left\lceil {F_{band}\left( \frac{r_{c}}{R_{ps}} \right)}^{2} \right\rceil},$

wherein F_(band) indicates bandwidth occupied by the primary system,R_(ps) indicates the radius of a cell, and r_(c) indicates the radius ofthe centre region of the cell (for example, r_(c)=0.65R_(ps)). Inaddition, F_(edge) ₁ =F_(edge) ₂ =F_(edge) ₃ =(F_(band)−F_(center))/3.Under this strategy, each primary user in the cell uses the sametransmission power.

FIG. 14 is a schematic diagram illustrating the soft FFR. In FIG. 14,each hexagonal block indicates one primary system cell. In eachhexagonal block, the circular region indicates the centre of the primarysystem cell, and the remaining part other than the circular regionindicates the edge of the primary system cell. Under this strategy,users at the edges of neighboring cells use different frequency bands,the frequency band used by a user at the edge of a cell is notoverlapped with the frequency band used by a user at the centre of thecell, and the frequency bands used by users located at the centre ofrespective cells are overlapped. As shown in the figure, F_(edge) ₁indicates a frequency band used by a user located at the edge of aprimary system cell 1; F_(edge) ₂ indicates a frequency band used by auser located at the edge of a primary system cell 2, 4 or 6; andF_(edge) ₃ indicates a frequency band used by a user located at the edgeof a primary system cell 3, 5 or 7. F_(center1) indicates a frequencyband used by a user located at the centre of the primary system cell 1;F_(center2) indicates a frequency band used by a user located at thecentre of the primary system cell 2, 4 or 6; and F_(center3) indicates afrequency band used by a user located at the centre of the primarysystem cell 3, 5 or 7. In this case, the magnitude of each F_(center),and the magnitude of each r_(c) are the same as those under the FFRstrategy, which are not repeated here. However, F_(edge) ₁ , F_(edge) ₂and F_(edge) ₃ are set as follows: F_(edge) ₁ =F_(edge) ₂ =F_(edge) ₃=min(┌F_(band)/3┐, F_(band)−F_(center)), and the transmission power of auser located at the edge of a cell is higher than the transmission powerof a user located at the centre of the cell.

FIG. 15 shows an example of a scenario that a secondary system islocated in multiple primary system cells. As shown in FIG. 15, a circleincluding a secondary system indicates the secondary system and otherhexagonal blocks indicate primary system cells. In FIG. 15, 27 primarysystem cells are shown, wherein the distance between each of the 27primary system cells and the secondary system is within coverage ofthree primary system cells, and the hexagonal blocks with oblique linesindicate 12 primary system cells closest to the secondary system. It canbe understood that, according to the distance between each primarysystem cell and the secondary system, the 12 cells located at the centreare cells having the biggest influence on the secondary system, whichare not described here in detail.

As a specific example, assuming that it is in a case that the secondarysystem is located in multiple primary system cells, the secondary systemcan know about distances between all transceivers in the primary systemand the secondary system (i.e., all nodes in the primary system and thesecondary system) (a secondary base station may adopt any suitablemethod to locate distances between the secondary base station and allnodes in the primary system and the secondary system, which is notdefined and described here in detail).

In a case that it is able to locate, the secondary system may obtain therelative positions between all transceivers (i.e., all nodes in theprimary system and the secondary system). The search interval and thevalue of T_(th) ^(h), may be obtained according to the FR strategy (forexample, the FFR strategy or the soft FFR strategy may be adopted whenthe primary system is the TD-LTE system) used by the primary system andthe method described above with reference to Formulas (A5) to (A8),which is not repeated here.

As another specific example, assuming that it is in a case that thesecondary system is located in multiple primary system cells, thesecondary system is unable to know about distances between alltransceivers in the primary system and the secondary system (that is, acase that it is unable to locate). In this case, the value of T_(th)^(h) may be obtained according to the FR strategy used by the primarysystem and the method described above with reference to Formulas (A9)and (A10), which is not repeated here.

Compared with the case of the single primary system cell, it isdifficult to obtain the search interval of the threshold value in thecase of multiple primary system cells. However, there is a need for theapproximate value of T_(th) ^(h) to be calculated in combination withthe FR strategy used by the primary system. As illustrated in Formula(5), the approximate value of T_(th) ^(h) is only related to the maximumvalue of the uplink transmission power. Therefore, under different FRstrategies, the power control and frequency allocation for the uplinktransmission are important factors that affect the value of T_(th) ^(h)in the case of multiple primary system cells.

FIG. 16 shows a case in which a secondary system coexists with 12primary system cells. Assuming that each primary system cell adopts theFFR strategy, then it can be considered that the power (the statistic)received by the secondary system increases by a specific coefficient F₁₂in this case. According to a distance between each primary system celland the secondary system and the path loss, the coefficient F₁₂ may becalculated with the following formula:

$\begin{matrix}{F_{12} = \frac{\left( {{3*\left( \sqrt{3} \right)^{\alpha}} + {3*\left( \frac{\sqrt{3}}{2} \right)^{\alpha}} + {6*\left( \sqrt{\frac{3}{7}} \right)^{\alpha}}} \right)}{\left( \sqrt{3} \right)^{\alpha}}} & ({A11})\end{matrix}$

Wherein α indicates a large-scale path attenuation factor. As a specificexample, when α=3.76, F₁₂=3.38.

In addition, under the FFR strategy, the number of the primary userssupported by each primary system is different from that in the case ofthe single primary system cell, and the bandwidth supported by eachprimary system cell is

$\left\lbrack {\left( \frac{r_{c}}{R_{ps}} \right)^{2} + \frac{1 - \left( {r_{c}/R_{ps}} \right)^{2}}{3}} \right\rbrack {F_{band}.}$

Therefore, in the case of multiple primary system cells, the approximatevalue of T_(th) ^(h) may be calculated with the following formula:

$\begin{matrix}{T_{th}^{h} = {\left( {{Var}_{n} + {{F_{12}\left\lbrack {\left( \frac{r_{c}}{R_{ps}} \right)^{2} + \frac{1 - \left( {r_{c}/R_{ps}} \right)^{2}}{3}} \right\rbrack}{PL}_{R_{ps}}P_{u_{\max}}}} \right)\left( {1 + \frac{Q^{- 1}\left( \overset{\_}{p} \right)}{\sqrt{n_{s}{N_{sc}/2}}}} \right)}} & ({A12})\end{matrix}$

Wherein PL_(R) _(ps) indicates path loss between the centre of a primarysystem cell (such as a primary system cell closet to the secondarysystem) and the centre of the secondary system cell, P_(u) _(max)indicates the uplink maximum total transmission power of the primarysystem. p indicates the probability that the

_(u) state is detected as the

_(d) state by mistake. It should be noted that, the probability p is notan actual probability but a reference value.

Similarly, under the scenario shown in FIG. 16, if the soft FR isadopted, then each primary system cell may use all frequency resources.Therefore, only the power control problem needs to be considered. Inthis case, the approximate value of T_(th) ^(h) may be calculated withthe following formula:

$\begin{matrix}{T_{th}^{h} = {\left( {{Var}_{n} + {\frac{2 + \varepsilon}{3\varepsilon}F_{12}{PL}_{R_{ps}}P_{u_{\max}}}} \right)\left( {1 + 1 + \frac{Q^{- 1}\left( \overset{\_}{p} \right)}{\sqrt{n_{s}{N_{sc}/2}}}} \right)}} & ({A13})\end{matrix}$

Wherein ε indicates transmission power ratio of a primary user locatedat the edge of the primary system cell to a primary user located at thecentre of the primary system cell.

Some embodiments for calculating the first threshold value and thesecond threshold value are described above. It should be understoodthat, these examples are exemplary. The disclosure is not limited tothese specific examples.

FIG. 4 shows another specific embodiment of the method used in acognitive radio system according to the disclosure. In this specificembodiment, after judging whether each channel resource occupied by thecommunication signal of the primary system is used for the uplinktransmission or the downlink transmission, the apparatus in thesecondary system may also use priori knowledge about standardconfigurations for the channel resource in the primary system to furtheroptimize the judgment result.

The standard configuration for the channel resource in the primarysystem refers to an uplink/downlink configuration type of the channelresource defined in a communication standard of the primary system. Thepriori knowledge about the standard configurations may be pre-stored inthe apparatus of the secondary system (for example, stored in a storagedevice of the apparatus (which is nor shown in the drawings)), which isnot described here in detail.

As shown in FIG. 4, the method is similar to the method shown in FIG. 1,and may include steps 402, 404 and 406. Steps 402, 404 and 406 arerespectively similar to steps 102, 104 and 106 shown in FIG. 1, whichare not repeated here. In addition, after step 406, the method furtherincludes a step 410. Specifically, at step 410, the judgment result instep 406 is matched with one or more standard configurations for thechannel resource in the primary system, to determine the uplink/downlinkconfiguration type of the channel resource in the primary system.

As an example, FIG. 5 shows 7 formats of uplink/downlink frameconfiguration defined in the TD-LTE standard. Still taking theapplication scenario shown in FIG. 3 as an example, assuming that theprimary system adopts the TD-LTE standard, then one of the 7 frameconfigurations shown in FIG. 5 should be adopted. As shown in FIG. 5,the TD-LTE standard adopts 7 frame configurations (which are indicatedby numbers 0 to 6). Each frame includes 10 sub-frames (which areindicated by numbers 0 to 9). D indicates a downlink sub-frame, Uindicates an uplink sub-frame, and S indicates a special sub-frame.After judging the uplink/downlink configuration for each sub-frame atstep 406, the apparatus in the secondary system may match the judgmentresult with these standard configurations, to further determine theformat of the uplink/downlink frame configuration for the primarysystem.

FIG. 6 shows an example for determining the uplink/downlinkconfiguration type of the channel resource according to the standardconfigurations for the channel resource. As shown in FIG. 6, at step410-1, the apparatus in the secondary system calculates a matchingdistance between the judgment result obtained at step 406 and eachstandard configuration; and then, at step 410-2, the apparatus in thesecondary system determines a standard configuration best matching thejudgment result according to the calculated matching distance. Forexample, a standard configuration having the smallest matching distancefrom the judgment result may be determined as the channel resourceconfiguration type of the primary system.

It should be understood that, any suitable method may be adopted tocalculate the matching distance between the judgment result and eachstandard configuration. Still taking the application scenario shown inFIG. 3 as an example, assuming that the primary system adopts the TD-LTEstandard, then one of the 7 standard frame formats shown in FIG. 5 isadopted. The secondary system may judge whether each sub-frame in aframe is an uplink sub-frame or a downlink sub-frame according to thereceived communication signal, and use for example two different numbersto indicate the judgment result on each sub-frame. For example, “1” maybe used to indicate a downlink sub-frame, and “−1” (or 0) may be used toindicate an uplink sub-frame; and vice versa. In this way, judgmentresults of the apparatus in the secondary system on multiple sub-framesin one frame may form a multi-dimensional vector. Each standard frameformat shown in FIG. 5 may also be indicated by a multi-dimensionalvector in the same manner. For example, D may be indicated as 1, and Umay be indicated as −1. In addition, the specific sub-frame “S” may alsobe indicated as a downlink sub-frame, that is because the first fewsymbols of the specific sub-frame are downlink sub-frames (in this case,the number of the symbols n_(s) used when the feature for judgingwhether each sub-frame is the uplink sub-frame or the downlink sub-frameis extracted is preferably less than 3). Therefore, the matchingdistance between the judgment result and each standard configuration maybe calculated with a method for calculating a distance between twovectors. It should be understood by those skilled in the art that, anysuitable method (such as an example describes hereinafter with referenceto Formula (21) or (22) or (26)) may be adopted to calculate thedistance between two vectors, which is not described here in detail.

With the method described above with reference to FIG. 4, the apparatusin the secondary system may utilize the priori knowledge about thestandard configurations for the channel resource in the primary system,to further optimize the judgment result on the uplink/downlinkconfiguration for the channel resource in the primary system, therebymaking the result more accurate.

In a specific embodiment, the apparatus in the secondary system mayjudge whether the channel resource is used for the uplink transmissionor the downlink transmission by utilizing features extracted frommultiple communication signals. In other words, when the uplink/downlinkconfiguration for the channel resource in the primary system is detectedwith the method described with reference to FIG. 1, 2 or 4, theapparatus in the secondary system may receive multiple communicationsignals (for example, a multi-frame signal is received when the primarysystem is a communication system based on time division transmission),and utilize the multiple communication signals to repeatedly perform theprocessing in steps 104 to 106 or steps 204 to 206 (or steps 204 to 208)or steps 404 to 406 (or steps 404 to 410). In this way, influence of arandom error event on the matching result is reduced in detecting eachsub-frame, thereby making the obtained result on the uplink/downlinkconfiguration for the channel resource more accurate.

In the embodiments and examples described above, a single apparatus inthe secondary system is adopted to detect the uplink/downlinkconfiguration for the channel resource in the primary system. In thefollowing, some embodiments that utilize multiple apparatuses in thesecondary system to judge the uplink/downlink configuration for thechannel resource and fuse judgment results from the multiple apparatusesare described. By utilizing multiple secondary users to cooperate,influence of space distribution of a single secondary user on theaccuracy of the detection result of the secondary user may be reduced,thereby making the obtained result on the uplink/downlink configurationfor the channel resource more accurate.

FIGS. 9(A), 9(B) and 9(C) respectively shows schematic models thatutilize multiple apparatuses in the secondary system to judge theuplink/downlink configuration for the channel resource and fuse judgmentresults from the multiple apparatuses, in which the application scenarioshown in FIG. 3 is taken as an example, and it is assumed that theprimary system is a communication system based on a time divisiontransmission mode. In addition, it is assumed that n_(id) indicates thenumber of the secondary users in the secondary system that participatein the detection, and n_(su) indicates the number of all secondary usersin the secondary system. The n_(id) secondary users may be divided inton_(d) groups, and the number of the secondary users in each group isn_(co)=n_(id)/n_(d). The detection may be performed by one secondaryuser, and may also be performed by multiple secondary users incooperation, therefore, 1≦n_(d)≦n_(id)≦n_(su).

In the model shown in FIG. 9(A), each secondary user may use a methoddescribed in the above or following embodiments or examples to: judgewhether the channel resource occupied by the communication signal isused for the uplink transmission or the downlink transmission, accordingto one or more features capable of reflecting the difference between auplink transmission mode and a downlink transmission mode for theprimary system that are extracted from the communication signal (block901 a in the figure, D_(i) ^((m)) is a vector, which includes theuplink/downlink judgment results of an i-th secondary user(su_(i)(1≦i≦n_(id)))) on all sub-frames of an m-th frame); and match thejudgment result with one or more standard configurations for the channelresource in the primary system, to determine the uplink/downlinkconfiguration type of the channel resource in the primary systemaccording to the matching result (block 902 a in the figure, t_(i) ^(m)indicates the determination result of the i-th secondary user(su_(i)(1≦i≦n_(id)))) on the m-th frame. Each secondary user may utilizedata of M frames to repeat the above processing (the processing shown inblocks 901 a and 902 a) for M times (“×M” shown in block 903 a), toobtain a determination result t_(i) of the i-th secondary user (su_(i)(1≦i≦n_(id))) on the frame configuration type. The determination resultsof these secondary users may be sent to one of the secondary users or tothe secondary base station to be fused, to further determine the frameconfiguration type of the primary system (block 904 a in the figure).

In the model shown in FIG. 9(B), each secondary user performs theuplink/downlink judgment for all sub-frames in an m-th frame (block 901b in the figure), and then sends all judgment results to one of thesecondary users or to the secondary base station to perform the fusion,to obtain a fused result D^((m)) (block 902 b in the figure, D^((m)) isa vector, which includes the uplink/downlink judgment results on allsub-frames in an m-th frame). Then, the fused result is matched with oneor more standard configurations for the channel resource in the primarysystem, to determine the uplink/downlink configuration type of thechannel resource in the primary system according to the matching result(block 903 b in the figure, for example, the frame configuration type ofthe m-th frame is obtained, which is indicated as T^((m))). Data of Mframes may be utilized to repeat the processing in blocks 901 b, 902 band 903 b for M times, and the results obtained after the processing isperformed M times are fused to determine the frame configuration type ofthe primary system (block 904 b in the figure).

The model shown in FIG. 9(C) is a combination of the models shown inFIGS. 9(A) and 9(B). Each secondary user performs the uplink/downlinkjudgment for all sub-frames in an m-th frame (as shown in block 901 c ofthe figure). These secondary users are divided into multiple groups, andthe judgment results of each group are sent to one of the secondaryusers or to the secondary base station to be fused, to further judge theuplink/downlink configuration for each sub-frame in the m-th frame (asshown in block 902 c of the figure). Then, the fused result of thejudgment results of each group is matched with each standardconfiguration, to obtain a matching result for each group (block 903 c).Data of M frames may be utilized to repeat the processing in blocks 901c, 902 c and 903 c for M times, and the results of the M times are fusedto determine the frame configuration type of the primary system (block904 c in the figure). Finally, the obtained multiple determinationresults are further fused, to determine the final frame configurationtype of the primary system (block 905 c in the figure).

In the following, some specific embodiments of a method for utilizingmultiple apparatuses in the secondary system to detect theuplink/downlink configuration for the channel resource in the primarysystem will be described. The method for fusing the judgment resultsfrom multiple secondary users that are shown in FIGS. 9(A), 9(B) and9(C) may refer to the specific embodiments described hereinafter.

FIG. 7 shows a specific embodiment of a method for detecting theuplink/downlink configuration for the channel resource in the primarysystem by utilizing multiple apparatuses in the secondary system.

As shown in FIG. 7, the method may include steps 702, 704, 706, 710, 712and 714.

Steps 702, 704 and 706 are similar to steps 102, 104 and 106 describedabove (or steps 202, 204 and 206, or steps 402, 404 and 406).Specifically, the apparatus in the secondary system (which is referredto as a first apparatus) receives a communication between respectiveapparatuses in the primary system; extracts, from the communicationsignal, one or more features that can reflect the difference between anuplink transmission mode and a downlink transmission mode for theprimary system; and judges whether the channel resource occupied by thecommunication signal is used for the uplink transmission or the downlinktransmission according to the extracted features, which is not describedhere in detail.

At step 712, the first apparatus receives judgment results about whetherthe channel resource occupied by the communication signal betweenapparatuses in the primary system is used for the uplink transmission orthe downlink transmission, from one or more other apparatuses (which isreferred to as a second apparatus) in the secondary system.

It should be understood that, each second apparatus may use the methodof steps 702 to 706 to judge whether the channel resource occupied bythe communication signal between respective apparatuses in the primarysystem is used for the uplink transmission or the downlink transmission,which is not repeated here.

Then, at step 714, the first apparatus judges whether the channelresource occupied by the communication signal is used for the uplinktransmission or the downlink transmission, according to the judgmentresult thereof and the judgment results from one or more secondapparatuses.

In the following, still taking the application scenario shown in FIG. 3as an example, an example of a method for fusing the judgment resultsfrom multiple apparatuses in the secondary system will be described.

It is assumed that n_(id) secondary users in the secondary system areutilized to judge (detect) whether the channel resource occupied by thecommunication signal of the primary system is used for the uplinktransmission or the downlink transmission, and that the primary systemis a TD-LTE system, and the standard frame configurations shown in FIG.5 are adopted. Each secondary user in the n_(id) secondary users mayadopt the method described above to generate a judgment result on eachsub-frame in one frame locally, that is, each secondary user obtains adeterministic judgment result on each sub-frame that is related to thethree states

_(d),

_(u) and

_(i). The judgment results of the n_(id) secondary users may be dividedinto multiple groups, in which each group includes the judgment resultsof n_(co) secondary users (n_(id)≧n_(co)). The judgment results of eachgroup may firstly be fused, and then the fused results of the multiplegroups are fused together.

As a specific example, the judgment results of the multiple secondaryusers may be sent to one of the secondary users (or sent to thesecondary base station in the secondary system), to be fused by thesecondary user (or the secondary base station).

As an example, the judgment result of each secondary user on eachchannel resource (such as each sub-frame) may be duality (the sub-frameis used for the uplink transmission or the downlink transmission), andthe duality judgment results of the multiple secondary users on thesub-frame uplink/downlink type may be fused directly.

As another example, the judgment result of each secondary user on eachchannel resource (such as each sub-frame) may be ternary (

_(d),

_(u) and

_(i)). The example may adopt the method described above with referenceto FIG. 2 that utilizes two threshold values. In the following, theexample is described by taking the application scenario shown in FIG. 3as an example. It is assumed that d_(i) indicates a judgment result on asub-frame that is obtained after an i-th secondary user (su_(i))compares an estimated energy value of the sub-frame that is estimated bythe i-th secondary user with the first threshold value T_(th) ^(h), andthe second threshold value T_(th) ^(l) (that is, the method for judgingthe uplink/downlink configuration for the channel resource by using twothreshold values that is described above with reference to FIG. 2 isadopted), that is:

$\begin{matrix}{d_{i} = \left\{ \begin{matrix}{2;} & {{{if}\mspace{14mu} T_{i}} \geq T_{th}^{t}} \\{1;} & {{{if}\mspace{14mu} T_{th}^{l}} < T_{i} < T_{th}^{h}} \\{0;} & {others}\end{matrix} \right.} & (8)\end{matrix}$

d_(i) in the above formula may be indicated with 2 bits. Assuming thatjudgment results of n_(co) secondary users are to be fused, then thejudgment results of the n_(co) secondary users on each sub-frame may beaccumulated. Assuming that n_(i) (i=0, 1, 2) indicates the number ofjudgment results whose d_(i) is respectively 0, 1 and 2 among thejudgment results of the n_(co) secondary users on a sub-frame, and then_(co) secondary users are the n-th group among the n_(id) secondaryusers participating in the detection, then the decision result D_(n) ofthis group of the secondary uses on the sub-frame may be obtained byfusing (such as accumulating) the judgment results of the n_(co)secondary users:

$\begin{matrix}\left\{ \begin{matrix}{{{H_{d}\mspace{14mu} {and}\mspace{14mu} D_{n}} = 1};} & {{{if}\mspace{14mu} {argmax}_{i}n_{i}} = 2} \\{{{H_{u}\mspace{14mu} {and}\mspace{14mu} D_{n}} = {- 1}};} & {{{if}\mspace{14mu} {argmax}_{i}n_{i}} = 1} \\{{{H_{i}\mspace{14mu} {and}\mspace{14mu} D_{n}} = {- 1}};} & {{{if}\mspace{14mu} {argmax}_{i}n_{i}} = 0}\end{matrix} \right. & (9)\end{matrix}$

That is, if the number of the judgment results which judge that asub-frame is 2 (downlink) is the biggest among the n_(co) judgmentresults on the sub-frame, then it is decided that the sub-frame is adownlink sub-frame, i.e., D_(n)=1. If the number of the judgment resultswhich judge that a sub-frame is 1 or 0 (uplink) is the biggest among then_(co) judgment results on the sub-frame, then it is decided that thesub-frame is a uplink sub-frame, i.e., D_(n)=−1.

The above decision may be performed on each sub-frame in one frame, toobtain decision results of each group of the secondary users on theuplink/downlink types of all sub-frames. The judgment results of an n-thgroup of the secondary users on all sub-frames of an m-th frame may beindicated as a vector D_(n) ^((m)), i.e., D_(n) ^((m)) includes thejudgment results of the n-th group of the secondary users on allsub-frames of the m-th frame.

In another example, it is assumed that {tilde over (d)}_(i) indicates ajudgment result on a sub-frame that is obtained after an i-th secondaryuser (su_(i)) of the n_(co) secondary users compares an estimated energyvalue of the sub-frame that is estimated by the i-th secondary user withthe second threshold value T_(th) ^(l), that is:

$\begin{matrix}{a_{i}^{\%} = \left\{ \begin{matrix}{{1\mspace{14mu} {if}\mspace{14mu} T_{i}} \geq T_{th}^{1}} \\{0\mspace{14mu} {otherwise}}\end{matrix} \right.} & (10)\end{matrix}$

Assuming that judgment results of the n_(co) secondary users are to befused, then the judgment results of the n_(co) secondary users on eachsub-frame may be accumulated, that is:

$\begin{matrix}\begin{matrix}{{{H_{d}\mspace{14mu} {and}\mspace{14mu} D_{n}} = 1};} & {{{{if}\mspace{20mu} n_{de}} \geq n_{th}^{h}},} \\{{{H_{u}\mspace{14mu} {and}\mspace{14mu} D_{n}} = {- 1}};} & {{{{if}\mspace{14mu} n_{th}^{I}} < n_{de} < n_{th}^{h}},} \\{{{H_{i}\mspace{14mu} {and}\mspace{14mu} D_{n}} = {- 1}};} & {{{{if}{\mspace{11mu} \;}n_{de}} \leq n_{th}^{,1}},}\end{matrix} & (11)\end{matrix}$

In the above formula, n_(de) indicates the number of the secondary userswhich detect a primary user signal in a sub-frame among the n_(co)secondary users, that is:

$\begin{matrix}{n_{de} = {\sum\limits_{i = 1}^{n_{co}}\; {\overset{\sim}{d}}_{i}}} & (12)\end{matrix}$

In Formula (11), n_(th) ^(h) indicates a threshold value (a thirdthreshold value) for further judging whether the sub-frame is an uplinksub-frame or a downlink sub-frame. That is, among the n_(co) secondaryusers, if the number of the secondary users which judge that a primaryuser signal exists in the sub-frame is more than n_(th) ^(h), then itmay decide that the sub-frame is a downlink sub-frame; otherwise, it maydecide that the sub-frame is an uplink sub-frame. After it is decidedthat the sub-frame is the uplink sub-frame, a threshold value n_(th)^(l) (a fourth threshold value) may be adopted to further determinewhether the uplink sub-frame is totally idle or a part of the uplinksub-frame is allocated to a sub-carrier of a primary user. Since thedownlink transmission power is relatively high, almost every secondaryuser may detect a primary user signal by utilizing the second thresholdvalue T_(th) ^(l). Therefore, the n_(th) ^(h) may be set as n_(co), orn_(co)−1. Whereas the n_(th) ^(l) may be set with reference to the valueof p_(f) ^(i). Since under the

_(i) state, the number of the secondary users which correctly detect the

_(i) state is n_(co)(1−p_(f) ^(i)), n_(th) ^(l) may be set to satisfyn_(th) ^(l)<n_(co)(1−p_(f) ^(i)) and keep a certain difference fromn_(th) ^(h). It should be understood that, any suitable method may beadopted by those skilled in the art to set the threshold valuesaccording to practical applications, and the disclosure is not limitedto the above examples.

The example of a hard information decision method (i.e., a dualityresult is adopted to indicate the judgment result of each group of thesecondary users on the sub-frame) that fuses the judgment results ofeach group of the secondary users (such as n_(co) secondary users) isdescribed above. Specifically, the numbers 1 and −1 are used to indicatewhether the sub-frame is an uplink sub-frame or a downlink sub-frame. Itshould be understood that, in practical applications, any dualitynumbers may be adopted to indicate the above judgment results, forexample, 1 and 0 and the like may be adopted, which is not enumeratedhere.

In the following, an example of a soft information decision method isdescribed. The soft information decision method described herein refersto that: the duality numbers are not used to indicate the decisionresult obtained after the judgment results of each group of thesecondary users (such as n_(co) secondary users) are fused, and anumerical interval is adopted to indicate the decision result. Differentpositions within the numerical interval corresponding to each sub-framereflect likely probability that the sub-frame is an uplink sub-frame ora downlink sub-frame. With this soft information decision method, theaccuracy of decision may be further improved. For example, in the aboveexample of the hard information decision method, the downlink sub-frameis indicated as “1”, and the uplink sub-frame is indicated as “−1”.Whereas in the soft information decision method, a difference between astatistic (such as an energy estimation value) on each sub-frame and athreshold value (such as the first threshold value) may be mapped into anumerical interval (such as [−1, 1] or [0, 1]). The smaller the mappedvalue of the difference within the numerical interval, the bigger theprobability that the sub-frame is an uplink sub-frame; otherwise, thebigger the probability that the sub-frame is a downlink sub-frame. Asanother specific example, a statistic (such as an energy estimationvalue) of each secondary user on each sub-frame may be compared with athreshold value (such as the first threshold value) to obtain adifference, and the differences obtained by the n_(co) secondary usersmay be averaged, then the obtained average value may be set as thedecision result obtained by fusing the judgment results of the group ofthe secondary users.

Assuming that T_(i)(1≦i≦n_(co)) is an energy estimation value of an i-thsecondary user among the n_(co) secondary users on a sub-frame, then anaverage value of the energy estimation values {tilde over (T)} of thesesecondary users may be indicated as:

$\begin{matrix}{\overset{\sim}{T} = {\sum\limits_{i = 1}^{n_{co}}{T_{i}/n_{co}}}} & (13)\end{matrix}$

The average value is compared with the threshold values T_(th) ^(l) andT_(th) ^(h) respectively. When {tilde over (T)}≦T_(th) ^(l), it isdecided that the sub-frame is in the

_(i) state; otherwise, {tilde over (T)}−T_(th) ^(h) is mapped into therange of [−1, 1] (other numerical intervals may also be adopted), andthe mapped value reflects the probability that the sub-frame is anuplink sub-frame or a downlink sub-frame. Since {tilde over (T)}ε[0,+∞), when the mapping is performed, a maximum value A and a minimumvalue B may be set to define a difference value interval which may beused for mapping. Any suitable mapping mode may be adopted, for example,the following mapping mode is adopted:

$\begin{matrix}\left\{ \begin{matrix}{{D_{n}^{\%} = \frac{T^{\%} - T_{th}^{h}}{T_{th}^{h} - B}}\mspace{14mu}} & {{{if}\mspace{14mu} B^{\%}} \leq T^{\%} < T_{th}^{h}} \\{{D_{n}^{\%} = \frac{T^{\%} - T_{th}^{h}}{A - T_{th}^{h}}}{\mspace{11mu} \;}} & {{{if}\mspace{14mu} T_{th}^{h}} \leq T^{\%} < A} \\{{D_{n}^{\%} = {- 1}}\mspace{11mu}} & {\; {{{if}\mspace{14mu} T^{\%}} < B}} \\{{D_{n}^{\%} = 1}\mspace{14mu}} & {otherwise}\end{matrix} \right. & (14)\end{matrix}$

In the above formula, {tilde over (D)}_(n) indicates a decision resultabout whether the sub-frame is an uplink sub-frame or a downlinksub-frame. As can be known from the above formula, when A is selected tobe big enough, there is a need for B to be selected to be small enough,so that Pr({tilde over (T)}>A) and Pr({tilde over (T)}<B) are smallenough, thereby making the mapping reasonable. On the other hand, Acannot be too big and B cannot be too small, otherwise, accuracy of themapping is influenced. When {tilde over (T)}≧T_(th) ^(h), it may beconsidered that the corresponding sub-frame is a downlink signal plus anoise signal. Since the downlink power is uniformly allocated to eachsub-carrier and is a constant value, {tilde over (T)} is only influencedby a complex noise signal. Therefore, the maximum A may be set tosatisfy the following relationship:

A=P _(d) PL _(R) _(ps) +αVar _(n)  (15)

In the above formula, α is constant. Preferably, α may be set as α=8, sothat Pr({tilde over (T)}>A) is small enough. Since the complex noisesample energy in this case is in exponential distribution, Pr({tildeover (T)}>A) will be very small when α∞8.

On the other hand, when {tilde over (T)}<T_(th) ^(h), it may be considerthat the sub-frame is an uplink signal plus a noise signal. Since theuplink signal power is not fixed and may be large or small, the value ofB may be decided by the noise power. Therefore, the value of B may bedetermined with the following formula:

B=βVar _(n)  (16)

That is, when {tilde over (T)}<B, it may consider that the sub-frame isan uplink sub-frame. β is constant, preferably, β may also be set as 8.It can be seen that T_(th) ^(l)<B by comparing T_(th) ^(l) with B. Thatis, the decision result is necessarily mapped to “−1” in the

_(i) state.

In the above example, the above decision may be performed on eachsub-frame in one frame, to obtain decision results of each group of thesecondary users on the uplink/downlink types of all sub-frames. Thedecision results of an n-th group of the secondary users on allsub-frames in an m-th frame may be indicated as a vector {tilde over(D)}_(n) ^((m)), and {tilde over (D)}_(m) ^((m)) includes the decisionresults of the n-th group of the secondary users on all sub-frames inthe m-th frame.

After the above fusing is performed, at step 710, the decision resultobtained at step 714 is matched with one or more standard configurationsfor the channel resource in the primary system, to determine theuplink/downlink configuration type of the channel resource in theprimary system. Step 710 is similar to the above described Step 410,which is not repeated herein.

Optionally, before the determining (step 710) is performed, credibilityof each judgment results may also be estimated, and a judgment resulthaving low credibility may be removed (the step shown in the dashed lineblock 718 in FIG. 7).

In the following, by taking the judgment results D_(n) ^((m)) of then-th group of the secondary users on all sub-frames in the m-th frame inthe above example as an example, an example of a method for estimatingthe credibility of the judgment result may be described. It is stillassumed that the primary system is the TD-LTE system, and 7 frameconfigurations shown in FIG. 5 are adopted. The 7 frame configurationsshown in FIG. 5 may be indicated by a matrix C with 7 rows and 10columns that is shown in the following formula:

$\begin{matrix}{C = \begin{bmatrix}1 & 1 & {- 1} & {- 1} & {- 1} & 1 & 1 & {- 1} & {- 1} & {- 1} \\1 & 1 & {- 1} & {- 1} & 1 & 1 & 1 & {- 1} & {- 1} & 1 \\1 & 1 & {- 1} & 1 & 1 & 1 & 1 & {- 1} & 1 & 1 \\1 & 1 & {- 1} & {- 1} & {- 1} & 1 & 1 & 1 & 1 & 1 \\1 & 1 & {- 1} & {- 1} & 1 & 1 & 1 & 1 & 1 & 1 \\1 & 1 & {- 1} & 1 & 1 & 1 & 1 & 1 & 1 & 1 \\1 & 1 & {- 1} & {- 1} & {- 1} & 1 & 1 & {- 1} & {- 1} & 1\end{bmatrix}} & (17)\end{matrix}$

In the above formula, each row represents one frame configuration shownin FIG. 5, in which “1” indicates a downlink sub-frame, and “−1”indicates an uplink sub-frame. In addition, as described above, thespecific sub-frame “S” shown in FIG. 5 also indicates a downlinksub-frame, that is because the first few symbols of the specificsub-frame are the downlink sub-frames (in this case, the number of thesymbols n_(s) used when the feature for judging whether each sub-frameis the uplink sub-frame or the downlink sub-frame is extracted ispreferably less than 3).

It can be known from the formula (17) that, in the matrix C, elements ineach column of the 0-th column to the second column, the fifth columnand the sixth column are the same as each other. Therefore, for eachrow, among 5 elements in the 0-th column to the second column, the fifthcolumn and the sixth column of D_(n) ^((m)), if more than s_(th)elements are same as the corresponding elements in C, then it may judgethat the detection results on the sub-frames in the m-th frame arecredible. For example, the credibility of D_(n) ^((m)) may be estimatedwith the following formula:

$\begin{matrix}{s = {\sum\limits_{{j = 0},1,2,5,6}\; {{D_{n}^{(m)}(j)}{C\left( {1,j} \right)}}}} & (18)\end{matrix}$

Wherein s indicates the credibility of D_(n) ^((m)). When the number ofelements among the 5 elements in D_(n) ^((m)), which are the same as thecorresponding elements in C is relatively large, the value of s isrelatively large; otherwise, the value of s is relatively small. Whens_(th) elements among the 5 elements are the same as the correspondingelements in C, s=1*s_(th)+(−1)*(5−s_(th))=2s_(th)−5. Therefore, whens≧2s_(th)−5, it may consider that the judgment result is credible,otherwise, the judgment result may be removed. In the example,considering that there are only 5 fixed sub-frame types in the matrix C,then s_(th) may be set as 3. s_(th) may also be referred to as a fifththreshold value. It should be understood that, the value of the fifththreshold value s_(th) may be determined according to practicalapplications, which should not be limited to the above example.

In the following, by taking the judgment results {tilde over (D)}_(n)^((m)) of the n-th group of the secondary users on all sub-frames in them-th frame in the above example as an example, an example of a methodfor estimating the credibility of the judgment result may be described.The credibility {tilde over (s)} of {tilde over (D)}_(n) ^((m)) may beestimated with the following formula:

$\begin{matrix}{\overset{\sim}{s} = {\sum\limits_{{j = 0},1,2,5,6}{\left( \overset{\sim}{\; D} \right)_{n}^{(m)}(j){C\left( {1,j} \right)}}}} & (19)\end{matrix}$

{tilde over (D)}_(n) ^((m)) ε[−1, 1], where a larger value indicateslarger probability that the sub-frame is a downlink sub-frame, and asmaller value indicates larger probability that the sub-frame is anuplink sub-frame. A larger value of {tilde over (s)} indicates that thevalue for representing the judgment result on the sub-frame in {tildeover (D)}_(n) ^((m)) is relatively correct, that is, the judgment result{tilde over (D)}_(n) ^((m)) is credible. {tilde over (s)} is notnecessarily an integer. As an example, in a case that {tilde over (s)}≧0is satisfied, it is considered that the judgment result {tilde over(D)}_(n) ^((m)) is credible.

FIG. 8 shows another specific embodiment of a method for utilizingmultiple apparatuses in the secondary system to detect theuplink/downlink configuration for the channel resource in the primarysystem.

As shown in FIG. 8, the method may include steps 802, 804, 806, 810, 812and 816.

Steps 802, 804, 806 and 810 are respectively similar to steps 402, 404,406 and 410 described above. Specifically, the apparatus in thesecondary system (which is referred to as a first apparatus) receives acommunication between apparatuses in the primary system; extracts, fromthe communication signal, one or more features that can reflect thedifference between an uplink transmission mode and a downlinktransmission mode for the primary system; judges whether the channelresource occupied by the communication signal is used for the uplinktransmission or the downlink transmission according to the extractedfeatures; and matches the judgment results with one or more standardconfigurations for the channel resource in the primary system, todetermine the uplink/downlink configuration type of the channel resourcein the primary system according to the matching result, which are notdescribed here in detail.

At step 812, the first apparatus receives determination results on theuplink/downlink configuration type of the channel resource in theprimary system, from one or more other apparatuses (which is referred toas a second apparatus) in the secondary system.

Optionally, after receiving the determination results from the secondapparatuses, the first apparatus may also estimate credibility of thedetermination result thereof and credibility of each of these receiveddetermination results, and remove a determination result having lowcredibility (as shown in the dashed line block 820 in FIG. 8). Thecredibility may be calculated with the example described above withreference to Formula (18) or (19) or an example described hereinafterwith reference to formula (23) or (27), which is not repeated here.

Then, at step 816, the first apparatus fuses the determination resultthereof and the determination results from one or more secondapparatuses, to determine the uplink/downlink configuration type of thechannel resource in the primary system. Specifically, multipledetermination results may be fused, a matching distance between thefused result and each standard configuration may be estimated, and theuplink/downlink configuration type of the channel resource in theprimary system is determined according to the matching distance.

Still taking the application scenario shown in FIG. 3 as an example, anexample of a method for fusing determination results of multipleapparatuses in the secondary system to determine the uplink/downlinkconfiguration type of the channel resource in the primary system isdescribed. It is still assumed that the primary system is the TD-LTEsystem, and the 7 frame configurations shown in FIG. 5 are adopted. Inaddition, it is still assumed that n_(id) secondary users in thesecondary system are utilized to determine the uplink/downlinkconfiguration type of the channel resource in the primary system. Thedetermination results of the n_(id) secondary users on each sub-framemay be divided into multiple groups, in which each group includes thedetermination results of n_(co) secondary users (n_(id)≧n_(co)). Thedetermination result of each group may be firstly fused, to obtain adecision result including the determination results of the n_(co)secondary users on all sub-frames in a frame. For example, the methoddescribed above with reference to the formula (9) or (14) may be adoptedto fuse the determination results of the n_(co) secondary users, toobtain a vector D_(n) ^((m)) (or {tilde over (D)}_(n) ^((m))). D_(n)^((m)) (or {tilde over (D)}_(n) ^((m))) is compared with each frameconfiguration shown in FIG. 5, and one frame configuration having thesmallest matching distance from D_(n) ^((m)) (or {tilde over (D)}_(n)^((m))) may be found.

As described above, the 7 configurations shown in FIG. 5 may constitutethe matrix C shown in formula (17).

Firstly, taking the vector D_(n) ^((m)) as an example, a specificexample for utilizing determination results of multiple apparatuses inthe secondary system to determine the uplink/downlink configuration typeof the channel resource in the primary system is described.

In an example, in order to calculate the matching distance between D_(n)^((m)) and each frame configuration, a difference between D_(n) ^((m))and each row in C (corresponding to one frame configuration) may befirstly calculated with the following formula:

S _(n) ^((m)) =I _(7×1) D _(n) ^((m)) −C  (20)

S_(n) ^((m)) indicates a difference matrix S_(n) ^((m)) between D_(n)^((m)) and C. I_(7×1) indicates a 7×1 unit matrix. As can be known fromthe formulas (17) and (18), only three kinds of elements are in S_(n)^((m)): “−2”, “0” and “2”. If an element S_(n) ^((m))(j, k) (0≦j≦6,0≦k≦9) is “2”, then it is indicated that the frame configuration is j (aj-th row in the matrix C), and the sub-frame k is misjudged as adownlink sub-frame; if S_(n) ^((m))(j, k) (0≦j≦6, 0≦k≦9) is “−2”, thenit is indicated that the frame configuration is j and the sub-frame k ismisjudged as an uplink sub-frame; and if S_(n) ^((m))(j, k) (0≦j≦6,0≦k≦9) is “0”, then it is indicated there is no misjudgment.

Then, the matching distance between D_(n) ^((m)) and each frameconfiguration in C may be calculated based on the number of variouselements in S_(n) ^((m)). In the following, two specific examples ofcalculating the mating distance are illustrated.

In one specific example, the matching distance may be calculated byutilizing a difference between D_(n) ^((m)) and each frameconfigurations in C. A vector is constituted by the matching distancesbetween D_(n) ^((m)) and each frame configurations in C, and isindicated as DI_(n) ^((m)). For example, DI_(n) ^((m)) may be calculatedby utilizing the number of nonzero elements (i.e., the number of timesthat an error decision occurs) in S_(n) ^((m)). The matching distanceDI_(n) ^((m))(j) (i.e., a j-th element in DI_(n) ^((m))) between D_(n)^((m)) and a j-th configuration type may be defined as:

$\begin{matrix}{\; {{{DI}_{n}^{(m)}(j)} = {\sum\limits_{{i = {- 2}},2}\; {N_{n}^{(i)}(j)}}}} & (21)\end{matrix}$

Wherein N_(n) ^(i)(j) indicates the number of non-zero elements in aj-th row in S_(n) ^((m)).

In another specific example, when the matching distance is calculated,an element “i” may be weighted, to show different effects of the nonzeroelements “−2” and “2” in calculating the matching distance. For example,the following formula may be adopted:

$\begin{matrix}{{{DI}_{n}^{(m)}(j)} = {\sum\limits_{i}\; {{N_{n}^{(i)}(j)}*w_{i}}}} & (22)\end{matrix}$

Wherein i=2, −2, 0; w_(i) indicates a weighting coefficient of anelement whose value is i; DI_(n) ^((m))(j) indicates the matchingdistance between D_(n) ^((m)) and a j-th configuration type; and N_(n)^(i)(j) indicates the number of non-zero elements in a j-th row in S_(n)^((m)), DI_(n) ^((m))(j) (0≦j≦6) constitute a vector DI_(n) ^((m)),which includes the matching distances between D_(n) ^((m)) andrespective frame configurations in C. A position of an element havingthe minimum value in DI_(n) ^((m)) corresponds to a frame configurationtype having a smallest matching distance from D_(n) ^((m)). Preferably,w₀=0, and w₂ and w⁻² may be set as different values. For example, it canmake w₂=w⁻², which indicates that the matching distance is proportionalto the number of the sub-frames whose types are different from eachother. For another example, w₂ may be different from w⁻², and the valuesthereof may be set with reference to error probability that an uplinksub-frame is misjudged as a downlink sub-frame or a downlink sub-frameis misjudged as an uplink sub-frame in sub-frame detection, therebyimproving the accuracy of matching. For example, if the probabilityP_(m) ^(d) that a downlink sub-frame is misjudged as an uplink sub-frameis less than the probability P_(f) ^(u) that an uplink sub-frame ismisjudged as a downlink sub-frame, then it is indicated that, in a rowcorresponding to a correct frame configuration type in S_(n) ^((m)), theprobability that element “−2” appears will less than the probabilitythat element “2” appears. Therefore, it can make w⁻²>w₂, to increase thematching distance between a frame configuration type that more “−2”appear and D_(n) ^((m)); otherwise, it can make w⁻²<w₂.

After the matching distance between the determination result and eachstandard configuration is obtained, a standard configuration having thesmallest matching distance from the determination result may bedetermined as the uplink/downlink configuration type of the channelresource in the primary system.

Optionally, after the matching distance between the determination resultand each standard configuration is estimated, it may further judgewhether a predetermined relationship is satisfied between the obtainedsmallest matching distance and a predetermined threshold value (which isreferred to as a sixth threshold value), if yes, then it is consideredthat a standard configuration corresponding to the smallest matchingdistance is the uplink/downlink configuration type of the channelresource in the primary system. For example, it is assumed that thesixth threshold value is denoted by W_(th), only if the smallestmatching distance is less than or equal to the threshold value, it isdetermined that the standard configuration corresponding to the smallestmatching distance is valid; otherwise, it is determined that thematching result is invalid. Taking the matching distance vector DI_(n)^((m)) in the above example as an example:

$\begin{matrix}\left\{ \begin{matrix}{{{N_{type}\left( {{argmin}_{j}{DI}_{n}^{(m)}} \right)} + 1};} & {{{if}\mspace{14mu} {minDI}_{n}^{(m)}} \leq W_{th}} \\{{The}\mspace{14mu} {matching}{\mspace{11mu} \;}{is}\mspace{14mu} {invalid}} & {otherwise}\end{matrix} \right. & (23)\end{matrix}$

N_(type) is a vector, which includes the number of times that eachstandard frame configuration is successfully matched which is obtainedafter the data of M frames has been utilized to perform the matching forM times. When the minimum element min DI_(n) ^((m)) in the vector DI_(n)^((m)) is less than or equal to the threshold value W_(th), it isconsidered that the corresponding frame configuration type is credible(that is, the corresponding element in N_(type) will increase by one(which is indicated by N_(type)(arg min_(j) DI_(n) ^((m)))+1 in theabove formula)); otherwise, it is considered that the matching isinvalid.

In addition, the following formula is obtained:

$\begin{matrix}{{t_{n}\left( {\arg {\max\limits_{j}N_{type}}} \right)} = 1} & (24)\end{matrix}$

Wherein t_(n) indicates a vector, in which a position of an elementwhich is “1” indicates the decision result of n_(co) secondary users inan n-th group on the frame configuration type. As described above,assuming that n_(id) secondary users participating in the detection aredivided into n_(d) groups, and each group includes n_(co) secondaryusers (n_(d)=n_(id)/n_(co)), then decision results of the n_(d) groupson the frame configuration type may be obtained, i.e., n_(d) vectorst_(n) (1≦n≦n_(d)). These decision results may be further fused, and afinal decision result may be obtained. For example, the final decisionresult may be calculated with the following formula:

$\begin{matrix}{T = {\arg \left( {\max\limits_{j}{\sum\limits_{n = 1}^{n_{d}}\; t_{n}}} \right)}} & (25)\end{matrix}$

Wherein T indicates the final decision result (i.e., the finallydetermined frame configuration type), that is, a frame configurationtype that most frequently appears in the n_(d) frame decision results isselected as the final frame configuration type.

In the following, taking the vector {tilde over (D)}_(n) ^((m)) as anexample, another specific example for utilizing determination results ofmultiple apparatuses in the secondary system to determine theuplink/downlink configuration type of the channel resource in theprimary system is described.

{tilde over (D)}_(n) ^((m)) adopts a soft information method, and thematching distance between {tilde over (D)}_(n) ^((m)) and each row inthe matrix C may be calculated with the following formula:

=C{tilde over (D)} _(n) ^((m)) ^(T)   (26)

Wherein

is a vector, and element values therein indicate the matching distancesbetween the vector {tilde over (D)}_(n) ^((m)) and respective standardframe configurations. It can be seen that, the more alike {tilde over(D)}_(n) ^((m)) is to a frame configuration, the larger thecorresponding element value in

is. This is opposite to DI_(n) ^((m)) in the example described withreference to Formulas (21) and (22). Therefore, a standard configurationcorresponding to an element with the maximum value in

may be determined as the uplink/downlink configuration type of thechannel resource in the primary system.

Optionally, it may also estimate whether a predetermined relationship issatisfied between the matching result obtained by the above Formula (26)and a predetermined threshold value (which is referred to as a sevenththreshold value), if yes, then it is considered that a standardconfiguration corresponding to the matching result is theuplink/downlink configuration type of the channel resource in theprimary system. For example, the following formula may be adopted:

$\begin{matrix}\left\{ \begin{matrix}{{{N_{type}\left( {{argmin}_{j}{\overset{\sim}{DI}}_{n}^{(m)}} \right)} + 1};} & {{{if}\mspace{14mu} \min {\overset{\sim}{DI}}_{n}^{(m)}} \leq {\overset{\sim}{W}}_{th}} \\{{The}\mspace{14mu} {matching}{\mspace{11mu} \;}{is}\mspace{14mu} {invalid}} & {others}\end{matrix} \right. & (27)\end{matrix}$

In the above formula, N_(type) is a vector, which includes the number oftimes that each standard frame configuration is successfully matchedwhich is obtained after the data of M frames has been utilized toperform the matching for M times. {tilde over (W)}_(th) indicates theseventh threshold value, and if the maximum element value in {tilde over(D)}_(n) ^((m)) is more than or equal to the threshold value, it isconsidered that the matching result is credible (i.e., the correspondingelement in N_(type), will increase by one (which is indicated byN_(type)(arg min_(j)

)+1 in the above formula)); otherwise, it is considered that thematching is invalid.

Some implementations of an apparatus used in a cognitive radiocommunication system according to the disclosure will be describedhereinafter.

FIG. 10 is a schematic block diagram illustrating a structure of anapparatus used in a cognitive radio system according to an embodiment.As shown in FIG. 10, the apparatus 1000 may include a receiving device1001, a feature extracting device 1002 and an uplink/downlink judgingdevice 1003. The apparatus 1000 may detect an uplink/downlinkconfiguration for a channel resource in a primary system with themethods in the embodiments or examples described above with reference toFIG. 1 and so on.

Specifically, the receiving device 1001 may be used to receive acommunication signal between respective apparatuses in the primarysystem, and provide the communication signal to the feature extractingdevice 1002.

The feature extracting device 1002 may be used to extract, from thecommunication signal received from the receiving device 1001, one ormore features that can reflect a difference between an uplinktransmission mode and a downlink transmission mode for the primarysystem, and provides the feature(s) to the uplink/downlink judgingdevice 1003. The feature extracting device 1002 may extract thefeature(s) with the methods in the embodiments or examples describedabove with reference to FIGS. 1 to 8. For example, the extractedfeatures may include at least one of a feature reflecting transmissionpower of the communication signal, a feature reflecting a modulationmode for the communication signal, and a peak-to-average ratio of thecommunication signal.

The uplink/downlink judging device 1003 may be used to judge whether thechannel resource occupied by the communication signal received by thereceiving device 1001 is used for uplink transmission or downlinktransmission, according to the feature(s) extracted by the featureextracting device 1002. The uplink/downlink judging device 1003 mayperform the judging with the methods in the embodiments or examplesdescribed above with reference to FIGS. 1 to 8.

The apparatus 1000 described above with reference to FIG. 10 utilizesthe communication signal received from the primary system to judge theuplink/downlink configuration for the channel resource in the primarysystem. There is no deed for the apparatus 1000 to perform informationinteraction with the primary system, therefore, there is no need for theprimary system to change its system configurations, which can bettermeet the requirement that the secondary system is transparent to theprimary system under the cognitive radio scenario.

The apparatus 1000 described above with reference to FIG. 10 may beequipped in a user apparatus (SU) in a cognitive radio system (which isalso referred to as the secondary system), and may also be equipped in abase station (SBS) in the secondary system.

As a specific embodiment, the apparatus 1000 may adopt the method shownin FIG. 2. The feature extracting device 1002 may be configured toestimate an energy value of the communication signal received by thereceiving device 1001 in the channel resource, as the feature capable ofreflecting the difference between the uplink transmission mode and thedownlink transmission mode for the primary system. The uplink/downlinkjudging device 1003 may be configured to judge whether a predeterminedrelationship is satisfied between the energy value estimated by thefeature extracting device 1002 and a predetermined threshold value (suchas the first threshold value described above), and if yes, then judgethat the channel resource is used for the downlink transmission.Specifically, the uplink/downlink judging device 1003 may judge whetherthe estimated energy value is greater than the first threshold value,and if yes, then judge that the channel resource is used for thedownlink transmission; otherwise, judge that the channel resource isused for the uplink transmission.

As an example, the first threshold value may be set according to themaximum uplink transmission power and the downlink transmission power ofthe primary system, which is not repeated here.

As another example, the uplink/downlink judging device 1003 maydetermine the first threshold value, for example, according to whetherthe secondary system can acquire relative position (such as distancesbetween respective nodes) information of all transceivers (i.e., allnodes) in the primary system and the secondary system. For example, ifthe secondary system can know about the relative position information(i.e., a case that the relative positions between respective nodes canbe located), the uplink/downlink judging device 1003 may estimate theaccuracy of the uplink/downlink detection, and then accurately set thefirst threshold value according to the accuracy. Alternatively, if thesecondary system can know about the relative position information (i.e.,a case that the relative positions between respective nodes can belocated), the uplink/downlink judging device 1003 may estimate a maximumvalue or a minimum value of the accuracy of the uplink/downlinkdetection, and calculate a feasible search interval of the firstthreshold value, and thereby search a suitable value within the searchinterval as the first threshold value. The uplink/downlink judgingdevice 1003 may determine the first threshold value with the methodsdescribed above with reference to Formulas (A1) to (A10), which is notrepeated here. When the secondary system can not know about the relativeposition information (i.e., a case that the relative positions betweenrespective nodes can not be located), the uplink/downlink judging device1003 may use a predetermined threshold value set according to themaximum uplink transmission power and the downlink transmission power ofthe primary system, as the first threshold value.

In the specific embodiment described above, the apparatus 1000 in thesecondary system utilizes the difference between the uplink transmissionpower and the downlink transmission power of the primary system to judgethe uplink/downlink configuration for the channel resource in theprimary system. Except for the downlink transmission power and themaximum uplink transmission power of the primary system, there is noneed for the secondary system to acquire other priori information aboutthe primary system to judge the uplink/downlink configuration, whichfacilitates the deployment of the secondary system.

Optionally, after judging that the channel resource is used for theuplink transmission by utilizing the energy value estimated by thefeature extracting device 1002, the uplink/downlink judging device 1003in the apparatus 1000 may further judge whether the uplink channelresource is idle. For example, the judgment may be performed byutilizing the processing described above with reference to the dashedline block 208 in FIG. 2, i.e., utilizing two threshold values (thefirst threshold value and the second threshold value), which is notrepeated here.

FIG. 11 is a schematic block diagram illustrating a structure of anapparatus 1100 for a cognitive radio communication system according toanother specific embodiment. Similar to the apparatus 1000, theapparatus 1100 also includes a receiving device 1101, a featureextracting device 1102 and an uplink/downlink judging device 1103;however, the apparatus 1100 differs from the apparatus 1000 in that theapparatus 1100 further includes a matching device 1104.

Functions of the receiving device 1101, the feature extracting device1102 and the uplink/downlink judging device 1103 are respectivelysimilar to the functions of the receiving device 1001, the featureextracting device 1002 and the uplink/downlink judging device 1003described above. The uplink/downlink configuration for the channelresource occupied by the communication signal of the primary system maybe judged with the methods described above with reference to FIGS. 4 to9, which is not repeated here.

The matching device 1104 may used to match the judgment result obtainedby the uplink/downlink judging device 1103 with one or more standardconfigurations for the channel resource in the primary system, todetermine the uplink/downlink configuration type of the channel resourcein the primary system according to the matching result. The matchingdevice 1104 may perform the matching with the methods in the embodimentsor examples described above with reference to FIGS. 4 to 9. For example,the matching device 1104 may calculate a matching distance between thejudgment result obtained by the uplink/downlink judging device 1103 andeach standard configuration, and determine a standard configuration bestmatching the judgment result according to the matching distance, as theconfiguration type of the channel resource in the primary system (steps410-1 and 410-2 shown in FIG. 6), which is not repeated here.

Similar to the apparatus 1000, the apparatus 1100 may also be configuredin a user apparatus (SU) in a cognitive radio system (which is alsoreferred to as the secondary system), and may also be configured in abase station (SBS) in the secondary system.

The apparatus 1100 in the secondary system may utilize priori knowledgeabout the standard configurations for the channel resource in theprimary system to further optimize the judgment result on theuplink/downlink configuration for the channel resource in the primarysystem, thereby making the result more accurate. The priori knowledgemay be, for example, stored in a storage device (which is not shown inthe figure) associated with the apparatus 1100. The storage device maybe a memory within the apparatus 1100, or may be an external storagedevice connected with the apparatus 1100 and accessible by the apparatus1100.

In a specific embodiment, the apparatus 1000 or 1100 in the secondarysystem may utilize features extracted from multiple communicationsignals to judge whether the channel resource is used for the uplinktransmission or the downlink transmission. Specifically, the receivingdevice 1001 or 1101 may receive multiple communication signals (such asmultiple frames), and the feature extracting device 1002 or 1102 mayrepeatedly perform the processing in step 104 or 204 or 404 to extractthe feature(s) described above from the multiple communication signals.The uplink/downlink judging device 1003 or 1103 may repeatedly performthe processing in step 106 or 206 or 406, and the matching device 1104may repeatedly perform the processing in step 410. In this way,influence of a random error event on the matching result may be reducedin detecting each sub-frame, thereby making the obtained result on theuplink/downlink configuration for the channel resource more accurate.

The embodiment or example described above provides a cognitive radiocommunication system (a secondary system), in which the apparatus 1000or 1100 is included, and the apparatus 1000 or 1100 is used to detect anuplink/downlink configuration for a channel resource in the primarysystem. The apparatus 1000 or 1100 may be a base station in thesecondary system, or may also be a user apparatus in the secondarysystem. The apparatus 1000 or 1100 may send the judgment result to otherapparatuses in the secondary system (for example, by utilizing a sendingdevice (which is not shown in the figure) in the apparatus 1000 or1100).

For example, if the apparatus 1000 or 1100 is a user apparatus in thesecondary system, then the user apparatus may utilize a sending devicethereof (which is not shown in the figure) to send the judgment resultthereof to a base station in the secondary system, and the judgmentresult is distributed to other user apparatuses by the base station.Alternatively, the apparatus 1000 or 1100 may utilize a sending devicethereof (which is not shown in the figure) to send the judgment resultthereof to other user apparatuses. Further, if the apparatus 1000 or1100 is a base station in the secondary system, then the base stationmay send the judgment result thereof to one or more user apparatuses inthe secondary system.

In other embodiments, the cognitive radio communication system (thesecondary system) may include multiple apparatuses 1000 or 1100, andutilize the multiple apparatuses to judge the uplink/downlinkconfiguration for the channel resource in the primary systemsimultaneously. The multiple apparatuses may respectively utilize thesending device thereof (which is not shown in the figure) to send thejudgment results thereof to one of the apparatuses, and these judgmentresults are fused by the apparatus. By utilizing the multipleapparatuses in the secondary system to cooperate, influence of the spacedistribution of a single apparatus on the accuracy of the detectionresult may be reduced, thereby making the obtained result on theuplink/downlink configuration for the channel resource more accurate.

In a specific embodiment, the receiving device (such as 1101) in anapparatus (such as 1100) in the secondary system may be furtherconfigured to receive determination results on the uplink/downlinkconfiguration type of the channel resource in the primary system, fromone or more other apparatuses (which is referred to as a secondapparatus) in the secondary system (such as step 812). The matchingdevice 1104 in the apparatus 1100 may be further configured to furtherdetermine the uplink/downlink configuration type of the channel resourcein the primary system, according to multiple determination results fromthe apparatus and the other apparatuses (the second apparatuses) and oneor more standard configurations for the channel resource in the primarysystem (such as the processing described with reference to step 816).The matching device 1104 may fuse the multiple determination results byadopting the method in the embodiment or the example described abovewith reference to FIG. 8 or 9, and finally determine the uplink/downlinkconfiguration type of the channel resource in the primary systemaccording to the fused result. For example, the matching device 1104 maybe further configured to, before fusing the multiple determinationresults, estimate credibility of each determination result, and remove adetermination result having low credibility (such as the processing instep 820). The matching device 1104 may perform the above operationswith the methods described above, which is not repeated here.

In another specific embodiment, the receiving device (such as 1001 or1101) in an apparatus (such as 1000 or 1100) in the secondary system maybe further configured to receive judgment results about whether thechannel resource occupied by the communication signal between respectiveapparatuses in the another radio communication system is used for theuplink transmission or the downlink transmission, from one or more otherapparatuses (the second apparatuses) in the secondary system (such asthe processing in step 712). The uplink/downlink judging device (such as1003 or 1103) may be further configured to determine whether the channelresource occupied by the communication signal of the primary system isused for the uplink transmission or the downlink transmission, accordingto the multiple judgment results of the apparatus and the otherapparatuses (the second apparatuses) (such as the processing describedwith reference to step 714). As a specific example, the uplink/downlinkjudging device (such as 1003 or 1103) may be further configured to,before fusing the multiple judgment results, estimate credibility ofeach judgment result, and remove a judgment result having lowcredibility (such as the processing in step 716). The uplink/downlinkjudging device (such as 1003 or 1103) may perform the above operationswith the methods in the embodiments or examples described above, whichis not repeated here.

As a specific embodiment, the feature extracting device (such as 1002 or1102) may be further configured to extract synchronization informationin the communication signal received by the receiving device (such as1001 or 1101), to locate channel resources occupied by the communicationsignal. Reference can be made to the processing described above withreference to step 203, and it is not repeated here.

In the above embodiments and examples, expressions such as “first” and“second” are adopted. It should be understood by those skilled in theart that, the expressions are only used to distinguish terms literally,and do not indicate sequence or any other limitation.

It should be understood that, the above embodiments and examples areexemplary other than being exhaustive, and it should not consider thatthe disclosure is limited by any specific embodiment or example.

As an example, each step in the method used in the cognitive radiosystem described above and each composition module and/or unit in theabove apparatus may be implemented in software, firmware, hardware or acombination thereof in the base station (SBS) or the user apparatus (SU)in the cognitive radio system, and the software, the firmware, thehardware or the combination thereof is used as a part of the basestation or the user apparatus. When each composition module and/or unitin the above apparatus are configured with the software, the firmware,the hardware or the combination thereof, specific available methods orways are well known for those skilled in the art, which IS not repeatedhere. As an example, the method and/or the apparatus according to thedisclosure may be implemented in an existing base station or an existinguser apparatus, as long as some modifications are made to each componentin the existing base station or the existing user apparatus.

As an example, in a case where it is implemented with the software orthe firmware, programs consisting of the software for implementing theabove method may be mounted, from a storage medium or network, onto acomputer (such as the general purpose computer 1200 shown in FIG. 12)having a dedicated hardware structure. When various programs aremounted, the computer can perform various functions.

In FIG. 12, a central processing unit (CPU) 1201 performs variousprocessing according to a program stored in a read only memory (ROM)1202 or a program loaded from a storage section 1208 to a random accessmemory (RAM) 1203. In the RAM 1203, data required when the CPU 1201performs various processing is also stored as necessary. The CPU 1201,the ROM 1202 and the RAM 1203 are connected with each other via bus1204. An input/output interface 1205 is also connected to the bus 1204.

The following components are linked to the input/output interface 1205:an input section 1206 (including a keyboard, a mouse and the like), anoutput section 1207 (including a display such as a cathode-ray tube(CRT) and a liquid crystal display (LCD), a speaker and the like), astorage section 1208 (including a hard disk and the like) and acommunication section 1209 (including a network interface card such as aLAN card, a modem and the like). The communication section 1209 performscommunication processing via a network such as internet. A driver 1201may also be linked to the input/output interface 1205 as necessary. Aremovable medium 1211, such as a magnetic disk, an optical disk, amagneto-optical disk and a semiconductor memory, may be mounted onto thedriver 1210 as necessary, so that a computer program read from theremovable medium 1211 may be mounted into the storage section 1208 asnecessary.

In a case where a series of processing described above is implemented bythe software, programs consisting of the software may be amounted from anetwork such as internet or a storage medium such as the removablemedium 1211.

It should be understood by those skilled in the art that, the storagemedium is not limited to the removable medium 1211 shown in FIG. 12which stores a program therein and distributes the program separatelyfrom the apparatus to provide the program to the user. An example of theremovable medium 1211 includes a magnetic disk (including a floppy disk(registered mark)), an optical disk (including a compact disc read onlymemory (CD-ROM) and a digital versatile disk (DVD)), a magneto-opticaldisk (including a mini disk (MD) (registered mark)) and a semiconductormemory. Alternatively, the storage medium may be a hard disk included inthe ROM 1202 or the storage section 1208 and the like, which stores aprogram therein and is distributed to the user together with theapparatus in which the storage medium is included.

The disclosure further provides a program product with a machinereadable instruction code stored thereon. The instruction code, whenbeing read and performed by a machine, may perform the above methodsaccording to the embodiments of the disclosure.

Accordingly, a storage medium used to carry the above program productwith a machine readable instruction code stored thereon is also includedin the disclosure. The storage medium includes, but is not limited to, afloppy disk, an optical disk, a magneto-optical disk, a memory card, amemory stick and the like.

In the above description of the specific embodiments of the disclosure,features described and/or illustrated for one embodiment may be used inone or more other embodiments in a same or similar way, combined withfeatures in other embodiments, or substitute features in otherembodiments.

It should be emphasized that, term “comprise/include”, when used herein,indicates the presence of a feature, an element, a step or a component,which does not exclude the presence or addition of one or more otherfeatures, elements, steps or components.

In addition, the method in the disclosure is not limited to be performedin the time sequence described in the specification, and may beperformed in other time sequences, in parallel or independently.Therefore, the execution sequence of the method described in thespecification should not be considered as limiting the technical scopeof the disclosure.

Although the disclosure has been disclosed above by the description ofthe specific embodiments of the disclosure, it should be understoodthat, all of the above embodiments and examples are exemplary ratherthan being restrictive. Various modifications, improvements orequivalents to the disclosure may be designed by those skilled in theart without deviation from the spirit and scope of the appended claims.It should be understood that, these modifications, improvements orequivalents are also within the scope of protection of the disclosure.

1. An electronic device, comprising: circuitry configured to detect anenergy value on a channel in a spectrum unlicensed to the electronicdevice; judge whether a predetermined relationship is satisfied betweenthe detected energy value and a first threshold to determine anoccupancy probability of the channel; and generate a report indicatingthe occupancy probability of the channel for facilitating a serving basestation of the electronic device to decide opportunistic utilization ofthe channel for communication.
 2. The electronic device according toclaim 1, wherein the circuitry is configured to: detect energy values ofone or more samples on the channel; and generate the report for theserving base station based on the energy values of the one or moresamples.
 3. The electronic device according to claim 2, wherein thecircuitry is configured to calculate an average value of the energyvalues of the one or more samples and include the average value in thereport.
 4. The electronic device according to claim 3, wherein eachsample corresponds to a symbol on the channel.
 5. The electronic deviceaccording to claim 1, wherein the circuitry is configured to determinethe channel is occupied under certain probability in case of thedetected energy value exceeding the first threshold.
 6. The electronicdevice according to claim 1, wherein an occupancy status of the channelcorresponds to one of downlink transmission occupied, uplinktransmission occupied or idle, and the circuitry is configured to judgewhether a predetermined relationship is satisfied between the detectedenergy value and a second threshold to distinguish the downlinktransmission occupied status and uplink transmission occupied status. 7.The electronic device according to claim 6, wherein the second thresholdvalue is set according to a maximum uplink transmission power and adownlink transmission power.
 8. The electronic device according to claim1, wherein the electronic device is implemented as a user equipment. 9.An electronic device, comprising: circuitry configured to detect anenergy value on a channel in a spectrum unlicensed to the electronicdevice; judge whether a predetermined relationship is satisfied betweenthe detected energy value and a first threshold to determine anoccupancy probability of the channel; acquire one or more reportsindicating the occupancy probability of the channel determined by one ormore other electronic devices; and decide opportunistic utilization ofthe channel for communication based on the occupancy probabilities. 10.The electronic device according to claim 9, wherein the report isgenerated by the other electronic device based on detection of energyvalues of one or more samples on the channel.
 11. The electronic deviceaccording to claim 10, wherein each report includes an average value ofthe energy values of the one or more samples.
 12. The electronic deviceaccording to claim 9, wherein the circuitry is configured to determinethe channel is occupied under certain probability in case of thedetected energy value exceeding the first threshold.
 13. The electronicdevice according to claim 9, wherein an occupancy status of the channelcorresponds to one of downlink transmission occupied, uplinktransmission occupied or idle, and the circuitry is configured to judgewhether a predetermined relationship is satisfied between the detectedenergy value and a second threshold to distinguish the downlinktransmission occupied status and uplink transmission occupied status.14. The electronic device according to claim 13, wherein the secondthreshold value is set according to a maximum uplink transmission powerand a downlink transmission power.
 15. The electronic device accordingto claim 9, wherein the circuitry is configured to merge the occupancyprobabilities to reduce judgment error of occupancy status of thechannel.
 16. The electronic device according to claim 9, wherein theelectronic device is implemented as a base station and the otherelectronic device is implemented as user equipment served by the basestation.
 17. A method in a radio communication system, comprising:detecting an energy value on a channel in a spectrum unlicensed to theelectronic device; judging whether a predetermined relationship issatisfied between the detected energy value and a first threshold todetermine an occupancy probability of the channel; and generating areport indicating the occupancy probability of the channel forfacilitating a serving base station of the electronic device to decideopportunistic utilization of the channel for communication.
 18. Themethod according to claim 17, wherein the method further comprisesdetecting energy values of one or more samples on the channel andgenerating the report for the serving base station based on the energyvalues of the one or more samples.
 19. The method according to claim 18,wherein the method further comprises calculating an average value of theenergy values of the one or more samples and include the average valuein the report.
 20. The method according to claim 19, wherein each samplecorresponds to a symbol on the channel.